Game reacts to controller input when in background

Platform, device version and operating system:

What you were expecting to happen, and what actually happened:
I usually have other games running at the same time as Gems of War. Sometimes, when Gems of War is in the background and the currently active game requires controller input, I return to Gems of War to find it in an entirely different state. Setting screen open with settings messed up, battles started and in progress, once even on the confirmation screen of an expensive real money purchase.

How often does this happen? When did it begin happening?
It happens often enough to make me close Gems of War whenever playing a controller based game. It has been happening for years now, every once in a while whenever didn’t remember to close Gems of War. It doesn’t happen every time, it might be triggered by special controller input sequence, e.g. pressing the start button. Keyboard input doesn’t get intercepted.

Steps to make it happen again
Play Gems of War, switch to another game that requires controller input, play that game long enough, switch back to Gems of War.