Plex is badly mangling import of a Music library

Even simpler: updating an Album Artist and Refreshing Metadata doesn’t work - this seems now a basic bug report. See below, and my attempts to get Plex to recognize when (for example) I fix a typo in Album artist and change CéU to Céu.
1.
plexb1
2.


3. FIX IN MP3TAG:
plexb3
4. REFRESH

5. REFRESH AGAIN

No change. No change. No change.

Plex simply isn’t updating Album Artist no matter how Metadata is supposedly refreshed. How can this be fixed?