You stopped the library update? It might be possible that this might have left some artists and albums in an undefined state.
Whenever something weird happens now, try first to refresh the artist.
If that doesn’t change anything, perform the Plex Dance “light” (i.e. without step 4) with all albums of the artist.
(Unless you have a lot of manually created playlists, which will lose all tracks from the “danced” albums.)
