Someone else was mentioning they were having issues with the YouTube editor, so my guess is they're working on something, and it's causing a bug somewhere. The music gallery in studio just got updated recently, and they have the studio classic version still open to allow people back in the old version in case there's features not available in the new version.
They're shutting down some features in playlists which is a studio classic feature which tells me they're getting ready to release the new studio version of playlists, and while I'm working on my closed captioning, that's all in studio classic, so it won't surprise me if that gets brought over to new studio soon as well.
I suspect all the bugs happening is far the backend of YouTube being modified recently.