[DaveBlake]

@BikerDude taking a look at the DB I can see nothing significantly wrong. You have some multiple artists that you have not given Kodi the taga data to be able to separate e.g. "Franz Bauer - Theussl & Wierner Volksopernoechestrer", and not sure how "The Dream Concert: Live from the Great Pyramids of Egypt - Yanni" is an artist but it will be a tagging issue.

The other link was a stacktrace, this has no use to me at all. A debug log file, created while Kodi was scanning the music source into the library might show something. That will be called kodi.log (located in the userdata folder) but you will need to turn debug logging on first and then scan the source into library before uploading it or the log file won't contain anything useful either.

My best guess so far is that you simply have not scanned all the music files into the library. I wonder if somehow in your tag editing you have set the file or folder permissions such that Kodi can not access all the music files. That would be one explanation, and it has happened to users before. Comparing your old db with your new I can see just in the "A"s  that the following folders are missing

"Z:\Ace of Base\"
"Z:\Adele\"
"Z:\Aerosmith\"
"Z:\Aisha Duo\"
"Z:\Alanis Morissette\"
"Z:\Alexandra Burke\"
"Z:\America\"
"Z:\Andrea Guerra\"
"Z:\Angie Stone\"
"Z:\Annie Lennox\"
"Z:\Antonello Venditti & Francesco De Gregori\"
"Z:\Antonio Vivaldi\"
"Z:\Ariel Ramírez; José Carreras\"

Anything you can spot in permissions on those compared to "Z:\ABBA\", "Z:\Andrea Bocelli\", "Z:\Andy Williams\" ?

Otherwise try to generate a debug log and I will see if that shows something. Turn debug on, rescan the music source using "scan to library" from the context menu when looking at music sources saying yes when asked "Do full tag scan even when music files are unchanged?".