Qt in debug (!) "lost" cocoa. What have I done?

Question

Qt

Tell me good people what and where I broke.
MacOS. Qt 5.5.1. qt creator. Suddenly when running any compiled app in debug crashes

This application failed to start because it could not find or load the Qt platform plugin "cocoa".

I know how they deal with this in release (macdeployqt), but then how?
Either he changed the path somewhere, or XCode was updated once again and screwed everything up, as usual.

Answer 1

The issue was resolved by reinstalling Qt and xCode (to be sure).