Any time I make any kind of change to a song (deleting it from the library, changing the rating, moving it to a playlist etc.) the song will change initially but then revert back to it's previous state after 5 seconds.
I had been working on this for a while and everything was functioning as expected and then all of a sudden none of my changes were sticking.
MacBook Air (13-inch, Early 2014), iOS 8.4