app runs fine on iphone 5 but apparently not on iphone 5S

Question

I just submitted my app to the app store last week and it got rejected yesterday. The reviewers apparently test on iphone 5S with iOS 7.0.4. They say the app does not load past the intro screen.

I have tested the app on iphone 5 and ipod touch 5th generation, both running the same operating system. On both it works perfectly fine.

Any ideas what could be the problem? It's a bit of an issue that I cannot test myself as the app uses the camera in the first screen and that's why immediately crashes when running in the simulator... but if I uncomment the camera setup it works in 64bit simulator...

edit: I am using C4 for most of my interface elements. So camera init looks like this

cam = [C4Camera cameraWithFrame:CGRectMake(0,0, self.canvas.width, self.canvas.height)];
cam.cameraPosition = CAMERABACK;
[self.canvas addCamera:cam];
[cam initCapture];