We are aware that some issues are causing lower end iOS devices (iPad 2 and iPad mini) to crash very frequently (every 5 minutes). We are looking into the causes of the issue and plan to have a fix included in our next update.
Something that might help. Ensure you are playing with no other apps running in the background. This should do something to reduce the crashing.
Keep an eye on this post for updates on when the fix will be released.
Sorry for any inconvenience.
Make a support ticket and tell us your device so we can look into it.
Support ticket created, iPhone 6
like the game ... hope stability can be improved
Our next update should greatly reduce this issue.