App Crashes when debugging on device

My application debugs fine on the iOS simulator, and it runs fine when I build and deploy an ipa file to the device. However, if I try to debug on the device (iPhone 9.3.1 and iPad 9.3), the app immediately crashes on startup. I am using Visual Studio w/ Xamarin. The problem seems to be build/configuration/version related since it works fine on the simulator and IPA file versions, but I just cannot figure out the problem.

Visual Studio 2013 Update 5 Xamarin 4.0.3.214 Xamarin.iOS 9.6.1.8

Project configurations between builds that work and don't:

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|iPhoneSimulator' ">
    <DebugSymbols>true</DebugSymbols>
    <DebugType>full</DebugType>
    <Optimize>false</Optimize>
    <OutputPath>bin\iPhoneSimulator\Debug</OutputPath>
    <DefineConstants>DEBUG</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
    <ConsolePause>false</ConsolePause>
    <MtouchDebug>True</MtouchDebug>
    <MtouchSdkVersion>8.1</MtouchSdkVersion>
    <MtouchArch>i386</MtouchArch>
    <MtouchOptimizePNGs>True</MtouchOptimizePNGs>
    <MtouchUseSGen>True</MtouchUseSGen>
    <MtouchUseRefCounting>True</MtouchUseRefCounting>
    <MtouchI18n>
    </MtouchI18n>
    <MtouchProfiling>True</MtouchProfiling>
    <MtouchLink>None</MtouchLink>
    <CodesignKey>iPhone Developer</CodesignKey>
    <CodesignProvision>
    </CodesignProvision>
    <CodesignExtraArgs>
    </CodesignExtraArgs>   
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|iPhone' ">
    <DebugSymbols>true</DebugSymbols>
    <DebugType>full</DebugType>
    <Optimize>false</Optimize>
    <OutputPath>bin\iPhone\Debug</OutputPath>
    <DefineConstants>DEBUG</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
    <ConsolePause>false</ConsolePause>
    <CodesignKey>iPhone Developer</CodesignKey>
    <MtouchSdkVersion>8.1</MtouchSdkVersion>
    <MtouchArch>ARMv7</MtouchArch>
    <MtouchOptimizePNGs>True</MtouchOptimizePNGs>
    <MtouchI18n>
    </MtouchI18n>
    <MtouchUseSGen>True</MtouchUseSGen>
    <MtouchDebug>True</MtouchDebug>
    <MtouchProfiling>True</MtouchProfiling>
    <SignAssembly>true</SignAssembly>
    <CodesignProvision>
    </CodesignProvision>
    <CodesignExtraArgs>
    </CodesignExtraArgs>   
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Ad-Hoc|iPhone' ">
    <DebugType>none</DebugType>
    <Optimize>True</Optimize>
    <OutputPath>bin\iPhone\Ad-Hoc</OutputPath>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
    <ConsolePause>False</ConsolePause>
    <CodesignKey>xxx</CodesignKey>
    <BuildIpa>True</BuildIpa>
    <MtouchSdkVersion>8.1</MtouchSdkVersion>
    <MtouchArch>ARMv7</MtouchArch>
    <MtouchOptimizePNGs>True</MtouchOptimizePNGs>
    <MtouchI18n>
    </MtouchI18n>
    <IpaPackageName>
    </IpaPackageName>
    <SignAssembly>true</SignAssembly>
    <CodesignProvision>xxx</CodesignProvision>
    <IpaMetadata>
    </IpaMetadata>
    <MtouchExtraArgs>
    </MtouchExtraArgs>
    <CodesignExtraArgs>
    </CodesignExtraArgs>   
</PropertyGroup>

Crash Report:

Incident Identifier: 3F2078C2-B276-4CCE-A5A0-43DCE3F4EB07
CrashReporter Key:   0ae3fc42ef86d1610013598af050cfcc24f778c2
Hardware Model:      iPhone7,2
Process:             RadResponder [3832]
Path:                /private/var/containers/Bundle/Application/30274A5D-271C-4E00-87B1-D3CE93033A8F/RadResponder.app/RadResponder
Identifier:          com.ChainbridgeTechnologies.RadResponder
Version:             45 (3.2.0)
Code Type:           ARM (Native)
Parent Process:      launchd [1]

Date/Time:           2016-04-20 09:41:34.34 -0600
Launch Time:         2016-04-20 09:41:31.31 -0600
OS Version:          iOS 9.3.1 (13E238)
Report Version:      105

Exception Type:  EXC_BAD_ACCESS (SIGABRT)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000084020400
Triggered by Thread:  0

Filtered syslog:
None found

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x20677c5c __pthread_kill + 8
1   libsystem_pthread.dylib         0x2071db47 pthread_kill + 63
2   libsystem_c.dylib               0x2060c0c5 abort + 109
3   RadResponder                    0x02e3a3e1 mono_handle_native_sigsegv (mini-exceptions.c:2186)
4   RadResponder                    0x02e405c9 mono_sigsegv_signal_handler (mini-runtime.c:2481)
5   libsystem_platform.dylib        0x2071985f _sigtramp + 43
6   RadResponder                    0x01f83fa0 System_Linq_Enumerable_ToArray_T_INT_System_Collections_Generic_IEnumerable_1_T_INT (Enumerable.cs:830)
7   RadResponder                    0x00de5d74 MvvmCross_Platform_iOS_Platform_MvxIosSystem_BuildVersion (/C:\vcs\git\MvvmCross\MvvmCross\Platform\iOS\Platform\MvxIosSystem.cs:27)
8   RadResponder                    0x00de5b38 MvvmCross_Platform_iOS_Platform_MvxIosSystem__ctor (/C:\vcs\git\MvvmCross\MvvmCross\Platform\iOS\Platform\MvxIosSystem.cs:22)
9   RadResponder                    0x01025628 MvvmCross_iOS_Platform_MvxIosSetup_CreateIosSystemProperties (/C:\vcs\git\MvvmCross\MvvmCross\iOS\iOS\Platform\MvxIosSetup.cs:114)
10  RadResponder                    0x01025514 MvvmCross_iOS_Platform_MvxIosSetup_RegisterPlatformProperties (/C:\vcs\git\MvvmCross\MvvmCross\iOS\iOS\Platform\MvxIosSetup.cs:109)
11  RadResponder                    0x0102538c MvvmCross_iOS_Platform_MvxIosSetup_InitializePlatformServices (/C:\vcs\git\MvvmCross\MvvmCross\iOS\iOS\Platform\MvxIosSetup.cs:100)
12  RadResponder                    0x0105c284 MvvmCross_Core_Platform_MvxSetup_InitializePrimary + 1532
13  RadResponder                    0x0105bc04 MvvmCross_Core_Platform_MvxSetup_Initialize + 120
14  RadResponder                    0x000bfaac RadResponder_Mobile_UI_iPhone_AppDelegate_FinishedLaunching_UIKit_UIApplication_Foundation_NSDictionary (/c:\tfs\rr\wksp\mbl-dev\RadResponder.Mobile.UI.iPhone\AppDelegate.cs:54)
15  RadResponder                    0x005689f4 wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr + 256
16  RadResponder                    0x02e42bff mono_jit_runtime_invoke (mini-runtime.c:2335)
17  RadResponder                    0x02e852a5 mono_runtime_invoke (object.c:2783)
18  RadResponder                    0x02dfcb6b native_to_managed_trampoline_6(objc_object*, objc_selector*, _MonoMethod**, objc_object*, objc_object*, char const*, char const*, char const*, char const*) (registrar.m:211)
19  RadResponder                    0x02dfc9bd -[AppDelegate application:didFinishLaunchingWithOptions:] (registrar.m:2962)
20  UIKit                           0x2502f8ff -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 395
21  UIKit                           0x252590bf -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 3087
22  UIKit                           0x2525d079 -[UIApplication _runWithMainScene:transitionContext:completion:] + 1589
23  UIKit                           0x25271649 __84-[UIApplication _handleApplicationActivationWithScene:transitionContext:completion:]_block_invoke3286 + 37
24  UIKit                           0x2525a59f -[UIApplication workspaceDidEndTransaction:] + 135
25  FrontBoardServices              0x220b7bf7 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 19
26  FrontBoardServices              0x220b7aa7 -[FBSSerialQueue _performNext] + 227
27  FrontBoardServices              0x220b7da5 -[FBSSerialQueue _performNextFromRunLoopSource] + 45
28  CoreFoundation                  0x209aba67 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
29  CoreFoundation                  0x209ab657 __CFRunLoopDoSources0 + 455
30  CoreFoundation                  0x209a99bf __CFRunLoopRun + 807
31  CoreFoundation                  0x208f8289 CFRunLoopRunSpecific + 517
32  CoreFoundation                  0x208f807d CFRunLoopRunInMode + 109
33  UIKit                           0x25028dc7 -[UIApplication _run] + 527
34  UIKit                           0x250232c5 UIApplicationMain + 145
35  RadResponder                    0x00aa5218 wrapper_managed_to_native_UIKit_UIApplication_UIApplicationMain_int_string___intptr_intptr + 272
36  RadResponder                    0x00a0e58c UIKit_UIApplication_Main_string___intptr_intptr (UIApplication.cs:77)
37  RadResponder                    0x00a0e54c UIKit_UIApplication_Main_string___string_string (UIApplication.cs:61)
38  RadResponder                    0x000bf204 RadResponder_Mobile_UI_iPhone_Application_Main_string__ (/c:\tfs\rr\wksp\mbl-dev\RadResponder.Mobile.UI.iPhone\Main.cs:12)
39  RadResponder                    0x005689f4 wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr + 256
40  RadResponder                    0x02e42bff mono_jit_runtime_invoke (mini-runtime.c:2335)
41  RadResponder                    0x02e852a5 mono_runtime_invoke (object.c:2783)
42  RadResponder                    0x02e885d1 mono_runtime_exec_main (object.c:4038)
43  RadResponder                    0x02ef5778 xamarin_main (monotouch-main.m:404)
44  RadResponder                    0x02e15261 main (main.armv7.m:158)
45  libdyld.dylib                   0x205a4873 start + 3

Thread 1:
0   libsystem_kernel.dylib          0x20678864 __workq_kernreturn + 8
1   libsystem_pthread.dylib         0x2071ae19 _pthread_wqthread + 1037
2   libsystem_pthread.dylib         0x2071a9fc start_wqthread + 8

Thread 2 name:  Dispatch queue: com.apple.libdispatch-manager
Thread 2:
0   libsystem_kernel.dylib          0x206792f8 kevent_qos + 24
1   libdispatch.dylib               0x2058b837 _dispatch_mgr_invoke + 255
2   libdispatch.dylib               0x2057d917 _dispatch_mgr_thread + 39

Thread 3:
0   libsystem_kernel.dylib          0x20678864 __workq_kernreturn + 8
1   libsystem_pthread.dylib         0x2071ae19 _pthread_wqthread + 1037
2   libsystem_pthread.dylib         0x2071a9fc start_wqthread + 8

Thread 4:
0   libsystem_kernel.dylib          0x20677da0 __recvfrom + 20
1   libsystem_c.dylib               0x205c7d5b recv + 23
2   RadResponder                    0x02ef3dcc recv_uninterrupted(int, void*, int) (monotouch-debug.m:387)
3   RadResponder                    0x02ef3fb0 monotouch_process_connection(int) (monotouch-debug.m:790)
4   RadResponder                    0x02ef2f5c monotouch_connect_usb() (monotouch-debug.m:697)
5   RadResponder                    0x02ef25e8 monotouch_configure_debugging (monotouch-debug.m:333)
6   RadResponder                    0x02edc8bc -[CocoaThreadInitializer entryPoint:] (shared.m:124)
7   Foundation                      0x2121662d __NSThread__start__ + 1145
8   libsystem_pthread.dylib         0x2071cc7f _pthread_body + 139
9   libsystem_pthread.dylib         0x2071cbf3 _pthread_start + 111
10  libsystem_pthread.dylib         0x2071aa08 thread_start + 8

Thread 5:
0   libsystem_kernel.dylib          0x20677998 __psynch_cvwait + 24
1   libsystem_pthread.dylib         0x2071c1a5 _pthread_cond_wait + 537
2   libsystem_pthread.dylib         0x2071d0b9 pthread_cond_wait + 41
3   RadResponder                    0x02ebeec5 thread_func (sgen-thread-pool.c:118)
4   libsystem_pthread.dylib         0x2071cc7f _pthread_body + 139
5   libsystem_pthread.dylib         0x2071cbf3 _pthread_start + 111
6   libsystem_pthread.dylib         0x2071aa08 thread_start + 8

Thread 6:
0   libsystem_kernel.dylib          0x20677da0 __recvfrom + 20
1   libsystem_c.dylib               0x205c7d5b recv + 23
2   RadResponder                    0x02ef3dcc recv_uninterrupted(int, void*, int) (monotouch-debug.m:387)
3   RadResponder                    0x02ef3ec8 sdb_recv(void*, int) (monotouch-debug.m:403)
4   RadResponder                    0x02e22a07 debugger_thread (debugger-agent.c:1515)
5   RadResponder                    0x02ed3927 inner_start_thread (mono-threads-posix.c:97)
6   libsystem_pthread.dylib         0x2071cc7f _pthread_body + 139
7   libsystem_pthread.dylib         0x2071cbf3 _pthread_start + 111
8   libsystem_pthread.dylib         0x2071aa08 thread_start + 8

Thread 7:
0   libsystem_kernel.dylib          0x206638f8 semaphore_wait_trap + 8
1   RadResponder                    0x02ed312b mono_sem_wait (mono-semaphore.c:109)
2   RadResponder                    0x02e644b7 finalizer_thread (gc.c:1096)
3   RadResponder                    0x02ea4d89 start_wrapper (threads.c:655)
4   RadResponder                    0x02ed3927 inner_start_thread (mono-threads-posix.c:97)
5   libsystem_pthread.dylib         0x2071cc7f _pthread_body + 139
6   libsystem_pthread.dylib         0x2071cbf3 _pthread_start + 111
7   libsystem_pthread.dylib         0x2071aa08 thread_start + 8

Thread 8:
0   libsystem_kernel.dylib          0x20678864 __workq_kernreturn + 8
1   libsystem_pthread.dylib         0x2071ae19 _pthread_wqthread + 1037
2   libsystem_pthread.dylib         0x2071a9fc start_wqthread + 8

Thread 0 crashed with ARM Thread State (32-bit):
    r0: 0x00000000    r1: 0x00000000      r2: 0x00000000      r3: 0x00000000
    r4: 0x00000006    r5: 0x376cd000      r6: 0xa10bb850      r7: 0x08721358
    r8: 0x15bc32ac    r9: 0x376cd908     r10: 0x0457fe7f     r11: 0x15bc3200
    ip: 0x00000148    sp: 0x0872134c      lr: 0x2071db47      pc: 0x20677c5c
  cpsr: 0x00000010

This isn't a direct answer to your question, but looking at the MvvmCross source for MvxIosSystem.BuildVersion, line 27 does appear to perform the ToArray where app dies on the invalid address access:

private void BuildVersion()
{
    var version = UIDevice.CurrentDevice.SystemVersion;
    var parts = version.Split('.').Select(int.Parse).ToArray();
    this.Version = new MvxIosVersion(parts);
}

Could UIDevice.CurrentDevice.SystemVersion be returning something interestingly unexpected by the MvvmCross framework?

I.e. how would version.Split('.').Select(int.Parse).ToArray() cause this invalid access?

Perhaps you could use a similar line of code in your app before the MvvmCross startup occurs to get the version value and hopefully more clues to debug with.

I tried this in a small Xamarin.iOS project, right in Main.cs, but couldn't see anything that would cause the problem - version came back "9.3.1" and parts was an array int[3]:

public class Application
{
    // This is the main entry point of the application.
    static void Main (string[] args)
    {
        //Xamarin.Insights.Initialize (XamarinInsights.ApiKey);
        var version = UIDevice.CurrentDevice.SystemVersion;
        var parts = version.Split('.').Select(int.Parse).ToArray();

        // if you want to use a different Application Delegate class from "AppDelegate"
        // you can specify it here.
        UIApplication.Main (args, null, "AppDelegate");
    }
}

I also tried substituting some creative values for version instead of calling UIDevice.CurrentDevice.SystemVersion, but all I could generate were unhandled string format or null reference exceptions with a very different iOS crash log than what you posted.

I wonder if device reset might clear the problem, from this SO answer to a similar question.