I've noticed something that recently crashes my game every now and then and I decided to report it since it ended up happening during a PVP match, causing me to lose 34 trophies. I'm using iOS.
I believe it happens when turning off the screen and then turning it back on, possibly while the device is moving or it thinks it has to change orientation. Moving may have nothing to do with it, but it seems to be confused about keeping it in landscape mode at least. The reason I think it might be related to oreintation changing is because, when the device wakes and shows the game, you can see half of it in portrait mode instead of landscape mode, with half of the game cut off and half of the screen black (since ML cannot be viewed in portrait mode).
When this happens, the game is not moving. Everything is frozen like a still image and the orientation cannot be changed. You have to restart the app. Or if you go back to the home screen and open the app again, it will restart it for you.