Please tell if you find the solution. I have pretty much the same problem with my Unity iOS app.

In my case, there was a problem with how Unity made the iOS build that would cause the load time at the beginning to be too long (it would never load and then the process would be shut down for taking too long). This problem did not show up during testing unless I turned off the debug executable. If you are using Unity try this solution. If you are not using Unity, the solution may still be relevant.