I found a solution to this along time ago, but forgot it and couldn’t find it when I got the problem again today.
The problem is: after I change the artist or album for certain MP3 tracks, as soon as I play them iTunes changes them back. I’ve got read and write access. I’ve used iTunes to convert to every version of the ID3 tag I could think of.
The solution turns out to be: remove the ID3 v1 tags. iTunes is only editing the v2 tags, and then reading the v1 tags and overwriting the v2 with that info. It’s totally weird and illogical but removing the v1 tags solves the problem.