Plex Music album art problems

When Plex Media Server scans my local music collection, it does a VERY poor job in matching album cover art to my albums. Anybody else have this problem, or better yet, knows a good solution?

I think my ID3 tags are in pretty good shape, I went through manually and cleaned things up (with some effort) via MP3tag. But, I’m seeing this happen with all kinds of music from all kinds of sources, including:
Digital copies of albums purchased through Amazon (and come with all the right tags)
CDs ripped using reputable CD burning software, that should be getting tags right when it does it (Exact Audio Copy)

There are like 4 or 5 different album covers that Plex is assigning, over and over again, to well over 70% of my collection.

Any thoughts on what is causing this and how I can fix it?

Additionally, to make matters worse, I’ve upgraded to a newer, bigger, better PMS box. And I transitioned from old to new in such a way that I kept all my old watched states and ratings for my movies. Which is a GREAT feature that Plex offers, and is able to carry over from machine to machine (love plex).

But I already manually fixed this once (click on the pen/pencil, and manually tell Plex what album art to use) on my old machine. And those (manual, time-intensive) cover-art choices did not carry over from last time. And neither did my music playlists. I have to rebuild all that from scratch.

Which is very disappointing… I want Plex to be my solution for local music… but this is frustrating.