It would also be OK to say, “Somehow, the playlists database got scrozzled. Sorry. If you do X (like delete all your playlists), your Roon server database will probably be back to a consistent state and you can start building playlists with confidence”.
As it stands, I tried to carefully build a new playlist from an old one, one track at a time, but allovasudden it ballooned up to a ridiculous number of hours. Unfortunately, I hadn’t checked the playlist after every addition, so I can’t produce a reproducible bug report. For some years, making reproducible bug reports was what I got paid to do. I’m not inclined to keep doing that work without some assistance/encouragement from @roonlabs.