Added music to playlist just disappears after a minute

I have had this problem for - literally - years now. I will add a new album to a playlist only to have those newly added tracks just disappear from the playlist and the music app altogether. I add them again and it usually sticks the second time. I have a lot of playlists and about 60,000 songs if that matters.

This happens with all new music. All the time. I keep thinking this bug will be fixed in an update - it hasn't.