Having the same problem in a project that I'm supposed to update to be allowed on app store, so lots of warnings that appear, then disappear again just as I go to check them out. It's crazy-making. I tried deleting build data, caches and everything suggested here. Also deleted and reinstalled XCode and all dependencies to no avail. Finally downloaded the latest 14.3 beta 2, and the bug hasn't been fixed. This shouldn't be happening after bug was first reported 5 months ago!