App Crashes Only On Testflight Build

Question

I have created an app on swift and tested it extensively using iPhone 6, iPhone 6 plus and iPhone 5 devices and all the simulators offered in Xcode. The app runs fine and do

Answer 1

I got it (partially!). Actually "release" implementation of UI_USER_INTERFACE_IDIOM() in swift project crashes the app.

However, still I have no clue why our app store app (objective c language based) does NOT crash.

My only guess is that it's a glitch in UI_USER_INTERFACE_IDIOM() API implementation with some language specific coding (swift vs objective c) by Apple.

Anyways, I would replace all UI_USER_INTERFACE_IDIOM() with UIDevice(). userInterfaceIdiom. I hope this helps someone!