Artwork for albums changes in the background (Apple Music)

I just upgraded to the latest OS (14.6.1). When I opened the Music App, some albums had their artwork changed. All albums by a particular band now have the artwork for the latest album I imported. I didn't sync with any other devices — I opened Music as soon as the system completed the upgrade.

This is the first time it's happened with an upgrade, but it happens a lot at other times. It may not be that *all* albums by an artist wind up with the same artwork, but I often find that artwork changes on its own.

What's going on? I really don't want to have to go through and change them all manually. And choosing Library>Get Artwork never seems to accomplish anything.