I have written an app, updated it to test flight and it works, but with some functionality broken in iCloud and the UI.
On the UI side I have slider that works perfectly in development, but is broken in test flight. I am unable to slide it, it seems disabled.
On the iCloud side I look for records more then 24 hours old and delete them, works perfectly in development, but does nothing in test flight.
And to be honest I am little lost as to how I can move forward on this. I don't want to try and publish it on the apps store, only to have the same issues... but how to debug this in test flight? It doesn't crash? there is no trace to look thru?
You can try to debug it when build for Release.
Change you scheme to Release, insert logs in the suspicious locations and run the app in X Code.
It's not going to be easy and fast, but that's nearly the only option you have.