iTunes Music Library Problems following migration to Music 1.1.4.110 & Big Sur 11.3.1

I'd like help, please, fixing a library of songs (mostly mp3's converted from CD's), and the management of new songs added to a library, that have recurring issues following a migration to Music 1.1.4.110 & Big Sur 11.3.1.

A few observations regarding problems within iTunes / Music:

1) Album art and lyrics of legacy songs are missing

2) info within legacy songs cannot be altered - changes (to genre, comments, changing album titles, etc) neither save to the songs within iTunes, nor within the file details on your local drive / folder taxonomy.

3) new .mp3 songs cannot be changed from original, input, file. No changes to album art, or song details, including, lyrics "stick" either, but rather always revert back to details of imported file.

I've done a lot of trouble-shooting - checking permissions, making sure all the info was in the previous files etc. It appears to be a problem with either Big Sur 11.3.1 or Music 1.1.4.110. or the combination of the two. I need a fix please! Thanks.