AppCertificationKit complains about exception that isn't thrown in debug mode

My UWP app doesn't pass the local app certification kit tests as the kit reports that there it throws an exception. I've checked the Windows Application Protocol and it reports an exception in Windows.UI.Xaml.dll with the code 0xc000027b at offset 0x6fce8b.

Unfortunately I have no clue what the problem actually is, as this exception is not thrown in Debug mode and the app also starts fine if I run it in Release mode from Visual Studio. I've read somewhere that this might be related to incorrectly working ValueConverters but I've gone through all of them and they don't return unexpected values or throw any exceptions.

I also haven't had any luck looking at the dumpfile. It doesn't contain any useful information that points me to the actual problem. (But I must admit I have no experience working with dumpfiles.)

What is the best way of finding out what's wrong? Can I safely assume it must be somethings in my XAML Markup? Or could it also be something of the code run in App.xaml.cs? What does the certification kit actually test? Does it just load the app or does it navigate within it? I've already thought about taking out all parts of the XAML on the first page, adding them step by step and running the certification after each step. But this would take ages, as the build process for Release is really really slow on my machine.