All solved on the support thread I opened.
To merge two artists, they both have to be in my library. So to solve the metadata/link issue I:
- went to the incorrect record for Stanton Mirands
- went to one of the two albums in her discography, and added that to my library
- went back to the merge process, and merged the two records
Interestingly, if I then remove the “Stanton Mirands” album from my library, the merge still holds and the metadata link remains fixed.
Thank you everyone for the help and suggestions.