Favorite songs keep disappearing

Occasionally, songs I add to favorites just disappear. It's not every song, but usually if I add a bunch of songs around 50 percent of them disappear and get unfavorited. Sometimes they come back to the playlist on their own; they just appear again randomly. They also come back to the playlist and get refavorited when I play the song. I've tried changing the setting on add favorites to library but that doesn't seem to change anything.