UWP App compiled with .NET native tool chain crashes on startup due to custom style

I have confirmed that the mere presence (even if it doesn't get used) of the following Style in a Xamarin Forms UWP project's App.xaml ResourceDictionary results in a crash on startup for the UWP app when compiled with .NET native tool chain enabled in release mode (x64, but don't think it matters in this case). Works 100% fine without .NET native tool chain enabled, but would really like to keep this custom style in AND reap the benefits of a faster app compiled natively. Does anybody know why it's crashing the app? I cannot even seem to figure out how to get a more detailed error message other than what I see in Windows event viewer, which just says Windows.UI.Xaml.dll is the faulting module name.

UPDATE: by turning "optimize code" off and enabling DEBUG in Release mode and running from VS, I was able to get the below.... which led me to an [great] animation library I was using called Xamanimation... still not sure the link between the custom style in my UWP app.xaml and this problem, but fixing this real problem of course solved everything (i.e. the style was a red herring). Added an answer on this below.

System.Private.Interop.dll!System.Runtime.InteropServices.McgMarshal.ThrowOnExternalCallFailed(int hr, System.RuntimeTypeHandle typeHnd) Line 1189 at f:\dd\ndp\fxcore\CoreRT\src\System.Private.Interop\src\Shared\McgMarshal.cs(1189)

System.ArgumentException HResult=0x80070057 Message=Value does not fall within the expected range. Source= StackTrace: StackTrace " at System.Runtime.InteropServices.McgMarshal.ThrowOnExternalCallFailed(Int32 hr, RuntimeTypeHandle typeHnd) in f:\dd\ndp\fxcore\CoreRT\src\System.Private.Interop\src\Shared\McgMarshal.cs:line 1189\r\n at __Interop.ComCallHelpers.Call(__ComObject __this, RuntimeTypeHandle __typeHnd, Int32 __targetIndex, Double arg0)\r\n
at __Interop.ForwardComStubs.Stub_22[TThis](__ComObject __this, Double value, Int32 __targetIndex)\r\n at Windows.UI.Xaml.IUIElement__Impl.Stubs.put_Opacity(__ComObject __this, Double value)\r\n at Windows.UI.Xaml.UIElement.put_Opacity(Double value)\r\n at Xamarin.Forms.Platform.UWP.VisualElementTracker2.UpdateOpacity(VisualElement view, FrameworkElement frameworkElement) in D:\\a\\1\\s\\Xamarin.Forms.Platform.UAP\\VisualElementTracker.cs:line 518\r\n at Xamarin.Forms.Platform.UWP.VisualElementTracker2.UpdateNativeControl() in D:\a\1\s\Xamarin.Forms.Platform.UAP\VisualElementTracker.cs:line 236\r\n at Xamarin.Forms.Platform.UWP.VisualElementTracker2.OnRedrawNeeded(Object sender, EventArgs e) in D:\\a\\1\\s\\Xamarin.Forms.Platform.UAP\\VisualElementTracker.cs:line 409\r\n at System.EventHandler1.Invoke(Object sender, TEventArgs e)\r\n at Xamarin.Forms.VisualElement.BatchCommit() in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:line 572\r\n at Xamarin.Forms.AnimationExtensions.HandleTweenerUpdated(Object o, EventArgs args) in D:\a\1\s\Xamarin.Forms.Core\AnimationExtensions.cs:line 274\r\n
at System.EventHandler.InvokeOpenStaticThunk(Object sender, EventArgs e)\r\n at System.EventHandler.Invoke(Object sender, EventArgs e)\r\n at Xamarin.Forms.Tweener.b__22_0(Int64 step) in D:\a\1\s\Xamarin.Forms.Core\Tweener.cs:line 92\r\n at System.Func2.Invoke(T arg)\r\n at Xamarin.Forms.Internals.Ticker.SendSignals(Int64 step) in D:\\a\\1\\s\\Xamarin.Forms.Core\\Internals\\Ticker.cs:line 136\r\n
at Xamarin.Forms.Internals.Ticker.SendSignals(Int32 timestep) in D:\\a\\1\\s\\Xamarin.Forms.Core\\Internals\\Ticker.cs:line 125\r\n
at Xamarin.Forms.Platform.UWP.WindowsTicker.RenderingFrameEventHandler(Object sender, Object args) in D:\\a\\1\\s\\Xamarin.Forms.Platform.UAP\\WindowsTicker.cs:line 25\r\n at System.EventHandler1.Invoke(Object sender, TEventArgs e)\r\n at __Interop.Intrinsics.HasThisCall__51(Object __this, IntPtr pfn, Object arg0, Object arg1)\r\n at __Interop.ReverseComStubs.Stub_41(Object __this, Void* unsafe_sender, Void* unsafe_args, IntPtr __methodPtr)" string

        <Style x:Key="FormTextBoxStyle" TargetType="uwp:FormsTextBox">
            <Setter Property="MinWidth" Value="{ThemeResource TextControlThemeMinWidth}" />
            <Setter Property="MinHeight" Value="{ThemeResource TextControlThemeMinHeight}" />
            <Setter Property="Foreground" Value="{ThemeResource SystemControlForegroundBaseHighBrush}" />
            <Setter Property="ForegroundFocusBrush" Value="{ThemeResource SystemControlForegroundChromeBlackHighBrush}" />
            <Setter Property="PlaceholderForegroundBrush" Value="{ThemeResource SystemControlPageTextBaseMediumBrush}" />
            <Setter Property="PlaceholderForegroundFocusBrush" Value="{ThemeResource SystemControlPageTextChromeBlackMediumLowBrush}" />
            <Setter Property="Background" Value="{ThemeResource SystemControlBackgroundAltHighBrush}" />
            <Setter Property="BackgroundFocusBrush" Value="{ThemeResource SystemControlBackgroundChromeWhiteBrush}" />
            <Setter Property="BorderBrush" Value="{ThemeResource SystemControlForegroundChromeDisabledLowBrush}" />
            <Setter Property="SelectionHighlightColor" Value="{ThemeResource SystemControlHighlightAccentBrush}" />
            <Setter Property="BorderThickness" Value="0,0,0,2" />
            <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}" />
            <Setter Property="FontSize" Value="{ThemeResource ControlContentThemeFontSize}" />
            <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Hidden" />
            <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Hidden" />
            <Setter Property="ScrollViewer.IsDeferredScrollingEnabled" Value="False" />
            <Setter Property="Padding" Value="0" />
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="uwp:FormsTextBox">
                        <Grid>
                            <Grid.Resources>

                                <Style x:Name="DeleteButtonStyle" TargetType="Button">
                                    <Setter Property="Template">
                                        <Setter.Value>
                                            <ControlTemplate TargetType="Button">
                                                <Grid
                                                    x:Name="ButtonLayoutGrid"
                                                    Background="{ThemeResource TextBoxButtonBackgroundThemeBrush}"
                                                    BorderBrush="{ThemeResource TextBoxButtonBorderThemeBrush}"
                                                    BorderThickness="{TemplateBinding BorderThickness}">
                                                    <TextBlock
                                                        x:Name="GlyphElement"
                                                        HorizontalAlignment="Center"
                                                        VerticalAlignment="Center"
                                                        AutomationProperties.AccessibilityView="Raw"
                                                        FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                                        FontSize="12"
                                                        FontStyle="Normal"
                                                        Foreground="{TemplateBinding Foreground}"
                                                        Text="&#xE10A;" />
                                                    <VisualStateManager.VisualStateGroups>
                                                        <VisualStateGroup x:Name="CommonStates">
                                                            <VisualState x:Name="Normal" />
                                                            <VisualState x:Name="PointerOver">
                                                                <Storyboard>
                                                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="GlyphElement" Storyboard.TargetProperty="Foreground">
                                                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAccentBrush}" />
                                                                    </ObjectAnimationUsingKeyFrames>
                                                                </Storyboard>
                                                            </VisualState>
                                                            <VisualState x:Name="Pressed">
                                                                <Storyboard>
                                                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ButtonLayoutGrid" Storyboard.TargetProperty="Background">
                                                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAccentBrush}" />
                                                                    </ObjectAnimationUsingKeyFrames>
                                                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="GlyphElement" Storyboard.TargetProperty="Foreground">
                                                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlHighlightAltChromeWhiteBrush}" />
                                                                    </ObjectAnimationUsingKeyFrames>
                                                                </Storyboard>
                                                            </VisualState>
                                                            <VisualState x:Name="Disabled">
                                                                <Storyboard>
                                                                    <DoubleAnimation
                                                                        Storyboard.TargetName="ButtonLayoutGrid"
                                                                        Storyboard.TargetProperty="Opacity"
                                                                        To="0"
                                                                        Duration="0" />
                                                                </Storyboard>
                                                            </VisualState>
                                                        </VisualStateGroup>
                                                    </VisualStateManager.VisualStateGroups>
                                                </Grid>
                                            </ControlTemplate>
                                        </Setter.Value>
                                    </Setter>
                                </Style>

                            </Grid.Resources>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="Auto" />
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                                <RowDefinition Height="*" />
                            </Grid.RowDefinitions>
                            <Border
                                x:Name="BackgroundElement"
                                Grid.Row="1"
                                Grid.RowSpan="1"
                                Grid.ColumnSpan="2"
                                Margin="{TemplateBinding BorderThickness}"
                                Background="{TemplateBinding Background}" />
                            <Border
                                x:Name="BorderElement"
                                Grid.Row="1"
                                Grid.RowSpan="1"
                                Grid.Column="0"
                                Grid.ColumnSpan="2"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                BorderThickness="{TemplateBinding BorderThickness}" />
                            <ContentPresenter
                                x:Name="HeaderContentPresenter"
                                Grid.Row="0"
                                Grid.Column="0"
                                Grid.ColumnSpan="2"
                                VerticalAlignment="Bottom"
                                VerticalContentAlignment="Bottom"
                                x:DeferLoadStrategy="Lazy"
                                Content="{TemplateBinding Header}"
                                ContentTemplate="{TemplateBinding HeaderTemplate}"
                                FontWeight="Normal"
                                Foreground="{ThemeResource SystemControlForegroundBaseHighBrush}"
                                Visibility="Collapsed" />
                            <ScrollViewer
                                x:Name="ContentElement"
                                Grid.Row="0"
                                Grid.RowSpan="2"
                                Grid.Column="0"
                                Margin="{TemplateBinding BorderThickness}"
                                Padding="{TemplateBinding Padding}"
                                VerticalAlignment="Center"
                                AutomationProperties.AccessibilityView="Raw"
                                Foreground="{TemplateBinding ForegroundFocusBrush}"
                                HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                                HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}"
                                IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}"
                                IsHorizontalRailEnabled="{TemplateBinding ScrollViewer.IsHorizontalRailEnabled}"
                                IsTabStop="False"
                                IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}"
                                VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
                                VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}"
                                ZoomMode="Disabled" />
                            <ContentControl
                                x:Name="PlaceholderTextContentPresenter"
                                Grid.Row="0"
                                Grid.RowSpan="2"
                                Grid.Column="0"
                                Grid.ColumnSpan="2"
                                Margin="{TemplateBinding BorderThickness}"
                                Padding="{TemplateBinding Padding}"
                                HorizontalAlignment="Left"
                                VerticalAlignment="Center"
                                Content="{TemplateBinding PlaceholderText}"
                                Foreground="{TemplateBinding PlaceholderForegroundBrush}"
                                IsHitTestVisible="False"
                                IsTabStop="False" />

                            <Button
                                x:Name="DeleteButton"
                                Grid.Row="1"
                                Grid.Column="1"
                                MinWidth="34"
                                Margin="{ThemeResource HelperButtonThemePadding}"
                                VerticalAlignment="Stretch"
                                BorderThickness="{TemplateBinding BorderThickness}"
                                FontSize="{TemplateBinding FontSize}"
                                Foreground="{TemplateBinding ForegroundFocusBrush}"
                                IsTabStop="False"
                                Style="{StaticResource DeleteButtonStyle}"
                                Visibility="Collapsed" />

                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup x:Name="CommonStates">
                                    <VisualState x:Name="Disabled">
                                        <Storyboard>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="HeaderContentPresenter" Storyboard.TargetProperty="Foreground">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledBaseLowBrush}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BackgroundElement" Storyboard.TargetProperty="Background">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledTransparentBrush}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BorderElement" Storyboard.TargetProperty="Background">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlBackgroundBaseLowBrush}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BorderElement" Storyboard.TargetProperty="BorderBrush">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledBaseLowBrush}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentElement" Storyboard.TargetProperty="Foreground">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledChromeDisabledLowBrush}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="PlaceholderTextContentPresenter" Storyboard.TargetProperty="Foreground">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource SystemControlDisabledChromeDisabledLowBrush}" />
                                            </ObjectAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualState>
                                    <VisualState x:Name="Normal" />

                                    <VisualState x:Name="PointerOver">
                                        <Storyboard>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BackgroundElement" Storyboard.TargetProperty="Opacity">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBackgroundHoverOpacity}" />
                                            </ObjectAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualState>
                                    <VisualState x:Name="Focused">
                                        <Storyboard>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="PlaceholderTextContentPresenter" Storyboard.TargetProperty="Foreground">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{Binding PlaceholderForegroundFocusBrush, RelativeSource={RelativeSource TemplatedParent}}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BackgroundElement" Storyboard.TargetProperty="Background">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{Binding BackgroundFocusBrush, RelativeSource={RelativeSource TemplatedParent}}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentElement" Storyboard.TargetProperty="Foreground">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="{Binding ForegroundFocusBrush, RelativeSource={RelativeSource TemplatedParent}}" />
                                            </ObjectAnimationUsingKeyFrames>
                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentElement" Storyboard.TargetProperty="RequestedTheme">
                                                <DiscreteObjectKeyFrame KeyTime="0" Value="Light" />
                                            </ObjectAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualState>
                                </VisualStateGroup>
                                <VisualStateGroup x:Name="ButtonStates">
                                    <VisualState x:Name="ButtonVisible">
                                        <Storyboard>

                                            <ObjectAnimationUsingKeyFrames Storyboard.TargetName="DeleteButton" Storyboard.TargetProperty="Visibility">
                                                <DiscreteObjectKeyFrame KeyTime="0">
                                                    <DiscreteObjectKeyFrame.Value>
                                                        <Visibility>Visible</Visibility>
                                                    </DiscreteObjectKeyFrame.Value>
                                                </DiscreteObjectKeyFrame>
                                            </ObjectAnimationUsingKeyFrames>

                                        </Storyboard>
                                    </VisualState>
                                    <VisualState x:Name="ButtonCollapsed" />
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

Apparently, this little hack using the Xamanimation library for adding an animation to some items on my ContentPage Appearing event does not work for the FadeToAnimation (although it works just fine for TranslateToAnimation):

    <xamanimation:StoryBoard x:Key="EntriesAnimation" Target="{x:Reference UserEntries}">
        <xamanimation:FadeToAnimation Opacity="0" Duration="0" />
        <xamanimation:FadeToAnimation Opacity="1" Duration="500" />
    </xamanimation:StoryBoard>

There were no issues with this in Debug mode, or in Release with .NET Native compilation disabled. But with it enabled, it was crashing the app.

The workaround was simple, I just set the Opacity property directly on the Target to 0 and got rid of the first line (<xamanimation:FadeToAnimation Opacity="0" Duration="0" />) and presto - everything was fine.