Exception in Viewport.Unproject after game restart

I have a simple android app with 2 activities – game mode selector and game activity. When I start game activity for the first time, everything is ok, but when I navigate back to selector and then again to game activity, game crashes on first call to GraphicsDevice.Viewport.Unproject.

What can cause such a behavior?

P.S. I implemented Unproject based on this gist – it works correctly, but the question remains – should I expect that other objects are corrupted after restart?

No, that shouldn’t happen. Do you have a stack trace?

No – almost every property in exception is null. Worth to say, I debug on device with Android 7.1 (API 25).