Hi
Here is an answer from programmers:
I've checked other case on my iPad 3rd gen, iPhone 5, 4S and on emulator on all devices - there is no problems with it. The problem is most probably connected with fact that iOS7 is not a good choice for iPhone 4 and it causes memory problems.
This is true, since I've upgraded I'm having problems with a lot of apps I've been using for a long time.
And an unfortunate solution:
If somebody will need a solution for IP4 with iOS7 you can always disable the animation scripts by detecting the IP4 (detecting the screen size and resolution - of course it will also detects the IP4S).