Created attachment 17990 [details]
Sample solution for checking the issue.
It seems that XAML compilation is causing this. When it is not used, the error does not manifest.
I attached a sample solution for checking.
fixed in https://github.com/xamarin/Xamarin.Forms/pull/718
in the meantime, you can get going by removing every static from your type converter so there's no static constructor generated, and you won't hit the bug
Should be fixed in 2.3.5-pre1. Thank you!