There seems to be a bug in iTunes 12.4 which causes playback issues with Apple Music tracks shorter than 60 seconds, MacRumors reported today.
The problem allegedly stems from a buffering bug that apparently causes iTunes to never begin downloading the next song in the queue if it's shorter than 60 seconds. Basically, iTunes is left waiting for a download to finish that has in fact never started. The bug has been reported to Apple and we expect it to be fixed in a future iTunes update.