After upgrading to iOS 26 I noticed that some of my Music artwork was wrong. I spent a while trying to fix it all, but there were too many so reluctantly decided to delete my entire Apple Music library on my Mac (100GB+ of MP3s built up over 20+ years) and start again from scratch. To my horror, this massive amount of effort did not fix the problem, half of the albums on my phone still have the incorrect artwork despite the artwork being correct both in Music on my Mac, and in the MP3 files themselves in Finder.

So far I have tried:

It seems there is some hidden cache of covers somewhere on either the phone or the Mac that I cannot get rid of, and have run out of ideas for how I can rectify this problem. Any other suggestions please?

And before anyone suggests it, I'm not interested in Apple Music, Spotify or any other streaming service, I have curated my digital music collection over the last 25+ years, mostly from CDs, and have no desire to move to streaming.

Any help much appreciated!