I've had songs disappear/reappear and I don't notice until it comes up on a discover/radio and I realize it isn't marked as liked anymore.

I imagine it's due to licensing fuckery, but you'd think they'd keep track of the song in your favourites and reinstate it later.. infuriating. I got part way through writing a script to periodically check what has disappeared earlier this year, maybe I should go dust it off