I discovered that some musicians have a biography of another person. The first was Ludvig van Bethoven, updated from the Gracenote data of premium lib. The second case is Gustav Mahler. I tried to re-match and checked that Allmusic have the correct bio. The issue is related to new Plex agent. Actual in all clients. Please fix it.
It’s only on “Classical” music (as far as I can see). Wolfgang Amadeus Mozart is another example.
No matter how many times you “Fix Match,” “UnMatch” or Plex Dance the artist and/or albums you get the same bio, obviously for “Iona Brown” You can even select her photo as the poster if you want. It should be noted, the albums are tagged with Mozart as the album artist, the tracks don’t have Iona Brown referenced in any way in the file name or metadata, and the file structure meets Plex requirements exactly. The albums are also matched properly, and available on the MusicBrainz website.
In my case, the albums were added after the old library was upgraded, so residual Gracenote data would have no bearing.