working out which version the tag or (most likely) tagS are stored in is a good starting point.
I know it'd be nice to do it all inside MB but... sometimes it's quicker and cleaner to use a dedicated tagger whose developer has spent only time on perfecting their tool (no jack of all trdes)
To which i suggest Tagscanner as it has an option that makes this task of unifying different contradicting id tags super easy by cross referencing from the original tags, writing new tags (acrooss the various versions of id tags &/or in the id format of your choice.
When updating all tags with a simple "save" click it insures 1 id tag version isn't returning a different set off info versus another version, causing you a headache ... in musicbee (which is an ok tag editor but, i'll leave it at but.)
Tagscanner comes in portable or installable format (x86 or 64bit variants) has a simple, neatly laid out ui and wont require pages of a manual to do basic things.
Has the usual lookup ooptions at discogs, musicbrainz etc & can also create m3u, cue files and if you wish to dig a little further even create text (rtf/txt) files displaying the info in your tags via simple scripts all produced at a click of a button to contain similar info you'd find at discogs. Handy for keeping info about the album/ep etc that you don't want to retain in your tags comment section or just wish to have ALL the info for future reference.