Now there is three versions of the playlist! Two of them is visable on my profile. One with no followers. The third one is the one that was attached to another user before. It now says that the playlist is mine but it is not connected to my profile or to the main playlist.
I have now deleted the duplicated playlists on my account. What is left to solve now is part of the original problem. My playlist has been divided into two, with lots of followers on each. I want them to be joined to one playlist again, as they were just a week ago.