I'm currently using iPad Mini MD530/RS with iOS 8.4 and every time I try to run the game, game shuts itself down after loading screen when tapped the Enter Vault option. I tried to restart the iPad several times but the result is the same.

I even tried to open a new Vault. It was okay in the beginning but when I expand my vault (more dwellers, more rooms) the app starts to behave in same way.

I also have this problem

what I've done is i have limited my new vault to 30 dwellers and it seems to work perfectly