Hi @Flukje,
Just popping in to confirm what @Slak_Jaw said. We recently released an update for djay Pro AI, version 4.0.2, that included a fix for a playback issue with Beatport and Beatsource tracks.
With this release, in order to provide a quicker fix for this playback issue, we had to temporarily disable the ability to edit playlists for these sources in djay. Our team is actively working on a proper fix for this that will re-enable playlist editing in a future update. We’ll keep you updated about that as it becomes available. Thanks in advance for your patience! 
