If you open the menu to concede while you’re in a game, after you’ve played while the AI is playing, sometimes the menu is really tiny. The controls are still active, but sized to the menu, so harder to hit.
Similarly, if you try to quit in the middle of the AI’s turn, the quit command registers but the dialog doesn’t go away, even if you tap Quit repeatedly; you have to tap Cancel and then the quit happens (or sometimes the game crashes).