1. It happens when playing a regular build your own prison game, after about an hour of playing. I currently have about 250 prisoners using a 60 % of a large map.
2. I have an iPad mini 2
3. I am running the latest version of the game
4. There are no other apps running at the time.
I have about 3 gigs of space left on my iPad, if that has anything to do with it. I am also running the latest iOS version as well. I update regularly.