I can see the problem with this now!
I have tracks by 'Agnelli & Nelson'.
They have an artist biography on last.fm at
https://www.last.fm/music/Agnelli+&+Nelson/+wikiBut using 'Artist Biography' setting on the 'now playing bar', MB changes it to "Agnelli and Nelson" which returns 'No artist biography' plus the artist pic shows the dreaded last.fm check-your-tags pic.
Checking my Last.fm account, the track is scrobbled properly as my tags are correct, but MB is converting the explicit
& in my tags to
and and I then don't get correct Artist Bio results.