Our Xamarin.Forms Android app crashes with the following error: "Register must call on startup(before use GetFormatter)."

In the App.xaml.cs OnStart() method we call:
MessagePack.Resolvers.CompositeResolver.RegisterAndSetAsDefault( MessagePack.Resolvers.GeneratedResolver.Instance, MessagePack.Resolvers.BuiltinResolver.Instance, AttributeFormatterResolver.Instance, MessagePack.Resolvers.PrimitiveObjectResolver.Instance );

Steps to Reproduce:

1. Start app via app icon => everything works fine
2. Send app to background by pressing home button
3. Open app again via app icon => App crashes with an InvalidOperationException "Register must call on startup(before use GetFormatter)."

We are using MessagePack 1.7.3.4.