Apple today released iTunes 12.4.2 with a fix for a bug that caused playback issues when listening to Apple Music tracks shorter than 60 seconds. Whenever a track shorter than 60 seconds was played, the next song would fail to play and cause a state of perpetual buffering.
This update resolves a playback issue with short Apple Music songs in your Up Next queue.
Today's iTunes update can be downloaded through the Software Update mechanism in the Mac App Store.
MacRumors readers first discovered the playback bug towards the end of June and MacRumors was able to replicate it on Macs running OS X 10.11.5 and iTunes 12.4.1. It appeared to be caused by the way Apple Music queues songs, preparing to stream the next song in a playlist or album when the current song was 60 seconds from the end. When a song was less than a minute long, the next song failed to initiate.