Yeap, I was right
There is a mis-match in the number of musicbrainz_albumartistID and albumartist, this causes the duplicate artist listing. For example you currently have
Artist: Phil Collins
Artists: Phil Collins
MUSICBRAINZ ARTIST ID: 401c3991-b76b-499d-8082-9f2df958ef78
AlbumArtist: Mark Mancina & Phil Collins
AlbumArtists:
MUSICBRAINZ ALBUM ARTIST ID: 628abc89-3e26-4e2c-b33f-67544ccbb72c / 401c3991-b76b-499d-8082-9f2df958ef78
Kodi sees "Mark Mancina & Phil Collins" as a single album artist, but scans the " / " to see 2 musicbrainz IDs. The tags need fixing for all that album's tracks, and it is probably worth checking any other album with multiple albumartists for the same issue. Musicbrainz database isn't perfect, things like this can happen.
You have a choice of how you fix this. Either
a) Change ALBUMARTIST to "Mark Mancina / Phil Collins" - note the space-slash-space.
But this will give you "Mark Mancina" and "Phil Collins" as separate
album artists, and displays "Mark Mancina / Phil Collins" when playing.
OR
b) Add ALBUMARTISTS tag (note the S) with value "Mark Mancina / Phil Collins"
This will also give you "Mark Mancina" and "Phil Collins" as separate
album artists, but will display "Mark Mancina & Phil Collins" when playing.
OR
c) Edit both the ALBUMARTIST and MUSICBRAINZ ALBUM ARTIST ID to both be one artist (assuming that you don't want both Phil and Mark in your album artist list). But having done this you must never scrape this in Isengard, or even look at the album info dialog, because the scraper will override the tag data and change the library. That bug is fixed in Jarvis, but even there if you enable tag override you will lose your changes. Messing with MBIDs is for grown-ups!
To be honest a) is the simplest, and then just live with having both Mark and Phil in your artist list (better than "Mark Mancina & Phil Collins" twice).
I will repeat: the number of items in the ALBUMARTIST and MUSICBRAINZ ALBUM ARTIST ID tag need to match. You will then see as many artists as you have musicbrainz IDs.