I sometimes get a window with Rollback Quit and so on. Is this a bug?
Maybe.
You should copy text or take screenshot, that should show what it is about.
Game sometimes gets confused and shows that screen, rollback or ignore often fix the situation.
Just hit ignore, constantly save your game since hitting ignore almost always works but you might get a surprise (at least that's how it is on PC, I'd like to believe it's the same on Android) :D
