Xamanimation | Xamarin Forms Animation Library | Animation library

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