Welcome to the quit bug, everyone! Sorry it's happening. Up until recently, it was an issue limited to just a few devices. Samsung Galaxy S3, S4, and some others.
Just something to try: Especially on my S3, which had it really bad, I found that Advanced Task Manager (for Android; maybe something similar for Apple) could be used to Close open apps. For me, it definitely correlated to having memory eaten up. AdvTaskManager also has a setting for Regular Kill, and I have mine set to kill programs every 60 seconds (that's the highest frequency). I also told it to show a screen footer every time it kills, so I can see that it's working while I play Dogfight (says something like Apps Killed, memory left ____).
I use this all the time on my S3, but haven't had to use it much recently on my S4. I don't know if this is the same problem, and actually I don't think Z knew much about what was happening before because it's third party software over which he has no control. But I hope it might help.
Manfred
Edit: Never mind, doesn't seem to be helping anyone. Wait for a re-release. Hopefully it will be soon, and working!