Xcode related.. but might pertain to Xojo for iOS

Has anyone ever tested an app, and had it freeze on the launchscreen?
I mean freeze to the point you have to reset the entire device (double tap Homekey does NOTHING)

This same app does the same thing in Simulator (under iOS9.3) BUT works perfectly under iOS12.1… and there is nothing in the app that is version specific.

AppDelegate never even seems to run…