I very carefully spend time curating my playlists. The ability to maintain my collections of songs is the primary reason I pay for spotify and I don't take this lightly.
So you can imagine my frustration at the fact that spotify has *continuously* modified my playlists on my behalf by deciding that two songs are "close enough" and replacing one with the other in my playlist.
Now, I can understand that song versions come and go. I get that if I add a version of a song to my playlist, it may later disappear because spotify loses the license to it.
But what is unacceptable is for spotify to decide it knows well enough to replace that version of a song with a totally different version of a song.
Here's a perfect example: spotify:track:31U21fwH5izi4fVA2f1HKa
When I added this song to my playlist, it was the version with the lyrics, a woman speaking over the backing track. Now this morning I went to play that song that I added to my playlist only to find that my playlist has been modified to point to a totally different version of the song, without the elements that drew me to add it in the first place.
This has happened many many times, and at first I thought I was crazy, but I know for absolute sure that spotify has been mutating my playlists without my permission.
Please, fix this bug. If a song loses license, then grey it out like you do already. But don't just decide you know well enough to say if two versions of a song are the same and modify my playlists. If I didn't care which songs I wanted to listen to, I wouldn't bother making playlists. At the very least, make it an option that I can opt into/out of.