I'M having same problem. In my case, position in game is saved and I can hit RESUME to bring the game back up and the clock will resume counting. Wasn't so bad once or twice a game but today been happening every few seconds. I thought this may be a way to get us to pay up but nothing is asked.
Thanks for the post. My game is also saved, and the clock is stopped. Please post if you discover a solution. I will also. I play on a Droid Ultra, BTW.