If a queue (ApplicationMusicPlayer.Queue) is set with both library and non-library (catalog) items, the queue will play only one kind of item (library or non-library) or will just stop playing when the next item is of a different kind.
Using both Xcode 16 beta 4 and Xcode 15.4. The issue was present in iOS 17 and is not resolved as of iOS 18 beta 4.
FB14491999