I think this is a bit awkward, if you call Navigation.showModal and during transition you press the physical back button, you get a white screen like your activity was removed from stack.
In the attached gif you can see it, on button press I'm calling showModal, if I press back on device, the result is I'm getting a white screen.

@guyca Any news on this? Can we help somehow through investigation?
I'm having the same issue!
I'm on 4.0.4 and this error is still happening
It's still happening with version 6.10.1
Hey @gaguirre I've prioritised this internally, hope to get to it in the next two weeks.
Great! Thank you @guyca and all the team!