Very strange WinDBG output for Windows Store (8.1) app

I've got a debug dump (available at http://1drv.ms/1CpYkmr), which gives me very strange output. I tried doing standard WinDBG stuff and got nothing useful, so I tried PDE.dll and got the following:

=========================================================================================
 PDE v9.5 - Copyright 2014 Andrew Richards
=========================================================================================
Start memory scan  : 0x0552e634 ($csp)
End memory scan    : 0x05530000 (User Stack Base)

0x0552e648 : 0x066dd578 :  !dse combase!STOWED_EXCEPTION_INFORMATION_V1
0x0552e650 : 0x066dd578 :  !dse combase!STOWED_EXCEPTION_INFORMATION_V1
0x0552e694 : 0x066dd578 :  !dse combase!STOWED_EXCEPTION_INFORMATION_V1
0x0552e6ec : 0x066dd578 :  !dse combase!STOWED_EXCEPTION_INFORMATION_V1
*** WARNING: Unable to verify checksum for System.Core.ni.dll

0:004> !PDE.dse
Stowed Exception Array @ 0x066dd578

Stowed Exception #1 @ 0x06728600
    0x80004003 (FACILITY_NULL - Default): E_POINTER - Pointer that is not valid

    Stack    : 0xb9505d4
        61e7f228 Windows_UI_Xaml!DirectUI::ButtonBase::ExecuteCommand+0x103
        61e7f469 Windows_UI_Xaml!DirectUI::ButtonBase::OnClick+0xc9
        621d87db Windows_UI_Xaml!DirectUI::Button::OnClick+0x9b
        61e8033b Windows_UI_Xaml!DirectUI::ButtonBase::PerformPointerUpAction+0x60
        61e80162 Windows_UI_Xaml!DirectUI::ButtonBase::OnPointerReleased+0x292
        620290be Windows_UI_Xaml!DirectUI::ControlGenerated::OnPointerReleasedProtected+0x7e
        61d5e28a Windows_UI_Xaml!DirectUI::Control::FireEvent+0x648bd5
        617159e4 Windows_UI_Xaml!DirectUI::DXamlCore::FireEvent+0x2cf
        617145c0 Windows_UI_Xaml!AgCoreCallbacks::FireEvent+0x40
        617144f7 Windows_UI_Xaml!CCoreServices::CLR_FireEvent+0xe7
        617143f5 Windows_UI_Xaml!CommonBrowserHost::CLR_FireEvent+0x35
        617126b0 Windows_UI_Xaml!CControlBase::ScriptCallback+0xe0
        61712a48 Windows_UI_Xaml!CXcpDispatcher::OnScriptCallback+0x21c
        617124c5 Windows_UI_Xaml!CXcpDispatcher::WindowProc+0x186
        75108e71 user32!_InternalCallWinProc+0x2b
        751090d1 user32!UserCallWinProcCheckWow+0x18e
        7510932c user32!DispatchClientMessage+0xdc
        75109529 user32!__fnDWORD+0x49
        77620996 ntdll!KiUserCallbackDispatcher+0x36
        7510e4a9 user32!SendMessageW+0x139
        61ace38b Windows_UI_Xaml!CXcpBrowserHost::SyncScriptCallbackRequest+0x11b
        617159ba Windows_UI_Xaml!CEventManager::Raise+0x4ba
        61acd396 Windows_UI_Xaml!CEventManager::RaiseRoutedEvent+0xd9
        61f070c7 Windows_UI_Xaml!CInputManager::RaiseDelayedPointerUpEvent+0x21c
        61f05419 Windows_UI_Xaml!CInputManager::ProcessGestureInput+0x279
        61f06e63 Windows_UI_Xaml!CInputManager::ProcessTouchInteractionCallback+0xc3
        61e2075b Windows_UI_Xaml!CCoreServices::ProcessTouchInteractionCallback+0x4b
        61ec80f5 Windows_UI_Xaml!CUIElement::TouchInteractionCallback+0x29
        61d8febe Windows_UI_Xaml!CTouchInteractionHelper::InteractionEngineCallback+0x5d5
        61d8ffb4 Windows_UI_Xaml!CTouchInteractionHelper::StaticInteractionEngineCallback+0x14
        6ae9a1ad ninput!COutputConverter::Process+0x1ec
        6ae99fa0 ninput!CInteractionContextImpl::OutputCallback+0x7c
        6ae99c09 ninput!CInteractionGroupingFilter::_SendOutput+0x29
        6ae99d4c ninput!CInteractionGroupingFilter::Input+0x2d
        6ae99cc5 ninput!COutputCoalescingFilter::Flush+0x49
        6ae99c64 ninput!CInteractionEngineImpl::DigitizerInput+0x4e4
        6ae97c21 ninput!ProcessInputInteraction+0x57
        6ae99605 ninput!CInteractionContextImpl::ProcessFrameHistory+0x998
        6aea08a4 ninput!ProcessPointerFramesInteractionContext+0x54
        61a013bb Windows_UI_Xaml!CTouchInteractionHelper::ProcessPointerInformation+0x1e3
        61a011c6 Windows_UI_Xaml!CTouchInteractionHelper::ProcessPointerMessage+0x66
        61a01696 Windows_UI_Xaml!CInputManager::ProcessPointerMessagesWithInteractionEngine+0x160
        61a05f08 Windows_UI_Xaml!CInputManager::ProcessInteractionPointerMessages+0x87
        61a05e65 Windows_UI_Xaml!CInputManager::ProcessPointerInput+0x771
        619ed303 Windows_UI_Xaml!CInputManager::ProcessInput+0xe5
        61acd81e Windows_UI_Xaml!CCoreServices::ProcessInput+0x3e
        61acd7a0 Windows_UI_Xaml!CXcpBrowserHost::HandleInputMessage+0x14a
        619ed5c4 Windows_UI_Xaml!CJupiterControl::HandlePointerMessage+0x62
        61bb7207 Windows_UI_Xaml!CJupiterControl::HandleWindowMessage+0x582fc3
        6163410f Windows_UI_Xaml!CJupiterWindow::WindowProc+0x114
        6163403b Windows_UI_Xaml!CJupiterWindow::StaticWindowProc+0x27
        75108e71 user32!_InternalCallWinProc+0x2b
        751090d1 user32!UserCallWinProcCheckWow+0x18e
        7510a66f user32!DispatchMessageWorker+0x208
        7510a6e0 user32!DispatchMessageW+0x10
        6aee3b6d Windows_UI!Windows::UI::Core::CDispatcher::WaitAndProcessMessages+0x16f
        6aee3c94 Windows_UI!Windows::UI::Core::CDispatcher::ProcessEvents+0x7a
        617d1348 Windows_UI_Xaml!DirectUI::FrameworkView::Run+0x87
        6b7b66ed twinapi_appcore!Windows::ApplicationModel::Core::CoreApplicationView::Run+0x3d
        6b7b6505 twinapi_appcore!Windows::Foundation::Collections::Internal::HashMap<unsigned int,Windows::UI::Core::ICoreWindow *,Windows::Foundation::Collections::Internal::DefaultHash<unsigned int>,Windows::Foundation::Collections::Internal::DefaultEqualityPredicate<unsigned int>,Windows::Foundation::Collections::Internal::DefaultLifetimeTraits<unsigned int>,Windows::ApplicationModel::Core::Details::SmugglableInterfaceLifetimeTraits,Windows::Foundation::Collections::Internal::HashMapOptions<unsigned int,Windows::UI::Core::ICoreWindow *,Windows::Foundation::Collections::Internal::DefaultLifetimeTraits<unsigned int>,0,1,0> >::Remove+0x215
        74674b16 SHCore!StringCchPrintfW+0x146
        77197c04 kernel32!BaseThreadInitThunk+0x24
        7763b54f ntdll!__RtlUserThreadStart+0x2f
        7763b51a ntdll!_RtlUserThreadStart+0x1b

Stowed Exception #2 @ 0x06728628
    0x80004005 (FACILITY_NULL - Default): E_FAIL - Unspecified failure

    Stack    : 0xb6d5dec
        61d36064 Windows_UI_Xaml!CDependencyObject::SetEffectiveValue+0x429027
        6190d5fb Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xd1
        6190d579 Windows_UI_Xaml!CDependencyObject::SetValue+0x55
        61716141 Windows_UI_Xaml!CUIElement::SetValue+0x61
        61716288 Windows_UI_Xaml!CFrameworkElement::SetValue+0x78
        6171cf47 Windows_UI_Xaml!CControl::SetValue+0x53
        6171d00b Windows_UI_Xaml!CContentControl::SetValue+0x77
        6194e9b0 Windows_UI_Xaml!CDependencyObject::SetThemeResourceBinding+0xba
        6184d3f2 Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xb72
        61867ff9 Windows_UI_Xaml!CFrameworkElement::OnStyleChanged+0x16b
        6186834e Windows_UI_Xaml!CControl::ApplyBuiltInStyle+0x48
        61895bee Windows_UI_Xaml!CControl::CreationComplete+0x7f
        61895b63 Windows_UI_Xaml!XamlManagedRuntime::InitializationGuard+0x12c
        6186220d Windows_UI_Xaml!XamlWriter::WriteNode+0x2e13
        61871bc3 Windows_UI_Xaml!CParser::LoadXamlCore+0x404
        618e31b0 Windows_UI_Xaml!CCoreServices::ParseXamlWithExistingFrameworkRoot+0xa0
        618e301d Windows_UI_Xaml!CApplication::LoadComponent+0x21c
        618e2dba Windows_UI_Xaml!Application_LoadComponent+0x95
        618e2ccb Windows_UI_Xaml!DirectUI::Application::LoadComponent+0xbb
        618e367d Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocationImpl+0x5d
        618e3608 Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocation+0x28
Unable to load image Windows.UI.Xaml.ni.dll, Win32 error 0n2
*** WARNING: Unable to verify checksum for Windows.UI.Xaml.ni.dll
*** ERROR: Module load completed but symbols could not be loaded for Windows.UI.Xaml.ni.dll
        6273101d Windows_UI_Xaml_ni+0x29101d

Stowed Exception #3 @ 0x06728650
    0x80004005 (FACILITY_NULL - Default): E_FAIL - Unspecified failure

    Stack    : 0x7e5b6d4
        61d36064 Windows_UI_Xaml!CDependencyObject::SetEffectiveValue+0x429027
        6190d5fb Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xd1
        6190d579 Windows_UI_Xaml!CDependencyObject::SetValue+0x55
        61716141 Windows_UI_Xaml!CUIElement::SetValue+0x61
        61716288 Windows_UI_Xaml!CFrameworkElement::SetValue+0x78
        6171cf47 Windows_UI_Xaml!CControl::SetValue+0x53
        6171d00b Windows_UI_Xaml!CContentControl::SetValue+0x77
        6194e9b0 Windows_UI_Xaml!CDependencyObject::SetThemeResourceBinding+0xba
        6184d3f2 Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xb72
        61867ff9 Windows_UI_Xaml!CFrameworkElement::OnStyleChanged+0x16b
        6186834e Windows_UI_Xaml!CControl::ApplyBuiltInStyle+0x48
        61895bee Windows_UI_Xaml!CControl::CreationComplete+0x7f
        61895b63 Windows_UI_Xaml!XamlManagedRuntime::InitializationGuard+0x12c
        6186220d Windows_UI_Xaml!XamlWriter::WriteNode+0x2e13
        61871bc3 Windows_UI_Xaml!CParser::LoadXamlCore+0x404
        618e31b0 Windows_UI_Xaml!CCoreServices::ParseXamlWithExistingFrameworkRoot+0xa0
        618e301d Windows_UI_Xaml!CApplication::LoadComponent+0x21c
        618e2dba Windows_UI_Xaml!Application_LoadComponent+0x95
        618e2ccb Windows_UI_Xaml!DirectUI::Application::LoadComponent+0xbb
        618e367d Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocationImpl+0x5d
        618e3608 Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocation+0x28
        6273101d Windows_UI_Xaml_ni+0x29101d

Stowed Exception #4 @ 0x06728678
    0x80004005 (FACILITY_NULL - Default): E_FAIL - Unspecified failure

    Stack    : 0x7e4fe5c
        61d36064 Windows_UI_Xaml!CDependencyObject::SetEffectiveValue+0x429027
        6190d5fb Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xd1
        6190d579 Windows_UI_Xaml!CDependencyObject::SetValue+0x55
        61716141 Windows_UI_Xaml!CUIElement::SetValue+0x61
        61716288 Windows_UI_Xaml!CFrameworkElement::SetValue+0x78
        6171cf47 Windows_UI_Xaml!CControl::SetValue+0x53
        6171d00b Windows_UI_Xaml!CContentControl::SetValue+0x77
        6194e9b0 Windows_UI_Xaml!CDependencyObject::SetThemeResourceBinding+0xba
        6184d3f2 Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xb72
        61867ff9 Windows_UI_Xaml!CFrameworkElement::OnStyleChanged+0x16b
        6186834e Windows_UI_Xaml!CControl::ApplyBuiltInStyle+0x48
        61895bee Windows_UI_Xaml!CControl::CreationComplete+0x7f
        61895b63 Windows_UI_Xaml!XamlManagedRuntime::InitializationGuard+0x12c
        6186220d Windows_UI_Xaml!XamlWriter::WriteNode+0x2e13
        61871bc3 Windows_UI_Xaml!CParser::LoadXamlCore+0x404
        618e31b0 Windows_UI_Xaml!CCoreServices::ParseXamlWithExistingFrameworkRoot+0xa0
        618e301d Windows_UI_Xaml!CApplication::LoadComponent+0x21c
        618e2dba Windows_UI_Xaml!Application_LoadComponent+0x95
        618e2ccb Windows_UI_Xaml!DirectUI::Application::LoadComponent+0xbb
        618e367d Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocationImpl+0x5d
        618e3608 Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocation+0x28
        6273101d Windows_UI_Xaml_ni+0x29101d

Stowed Exception #5 @ 0x067286a0
    0x80004005 (FACILITY_NULL - Default): E_FAIL - Unspecified failure

    Stack    : 0x7dfa064
        61d36064 Windows_UI_Xaml!CDependencyObject::SetEffectiveValue+0x429027
        6190d5fb Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xd1
        6190d579 Windows_UI_Xaml!CDependencyObject::SetValue+0x55
        61716141 Windows_UI_Xaml!CUIElement::SetValue+0x61
        61716288 Windows_UI_Xaml!CFrameworkElement::SetValue+0x78
        6171cf47 Windows_UI_Xaml!CControl::SetValue+0x53
        6171d00b Windows_UI_Xaml!CContentControl::SetValue+0x77
        6194e9b0 Windows_UI_Xaml!CDependencyObject::SetThemeResourceBinding+0xba
        6184d3f2 Windows_UI_Xaml!CDependencyObject::UpdateEffectiveValue+0xb72
        61867ff9 Windows_UI_Xaml!CFrameworkElement::OnStyleChanged+0x16b
        6186834e Windows_UI_Xaml!CControl::ApplyBuiltInStyle+0x48
        61895bee Windows_UI_Xaml!CControl::CreationComplete+0x7f
        61895b63 Windows_UI_Xaml!XamlManagedRuntime::InitializationGuard+0x12c
        6186220d Windows_UI_Xaml!XamlWriter::WriteNode+0x2e13
        61871bc3 Windows_UI_Xaml!CParser::LoadXamlCore+0x404
        618e31b0 Windows_UI_Xaml!CCoreServices::ParseXamlWithExistingFrameworkRoot+0xa0
        618e301d Windows_UI_Xaml!CApplication::LoadComponent+0x21c
        618e2dba Windows_UI_Xaml!Application_LoadComponent+0x95
        618e2ccb Windows_UI_Xaml!DirectUI::Application::LoadComponent+0xbb
        618e367d Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocationImpl+0x5d
        618e3608 Windows_UI_Xaml!DirectUI::ApplicationFactory::LoadComponentWithResourceLocation+0x28
        6273101d Windows_UI_Xaml_ni+0x29101d

I might be interpreting the stacktrace wrong, but it looks to me like it's failing inside Windows.UI.Xaml when trying to call ExecuteCommand. It doesn't look like it's my actual command that's failing, but not even managing to get there.

It's a standard store app that passed WACK, it's live on the store and I've not done anything weird. It's a combination of C# and F#, but the entire UI/XAML stuff is C#.

Completely stumped at this point, not sure what to do.