I do see one problem here, there should be no spaces in the actual Artistsort and Albumartistsort field names.
Or if you are keeping these fields due to your file or player’s preference, make sure you add the spaces into the action field (not the ones in the drop down list that don’t have spaces).
Cheers, Motley.
I think it's worked on one CD I just tested. ArtistSort and AlbumArtistSort have been removed. There is not a preset for ConductorSort and ComposerSort - but I'll try creating my own . . .
Paul
. . . I'll try Composer and Conductor SORT without spaces, as you helpfully observed. THANKS.
Not sure this is an “official” tag field that will be supported by any players. But you are free to create just about any field you want for your own reference!
You can find the various supported tags here
MASSIVE THANKS to Motley and ohrenkino! 
I think I'm finally there now. It took a while to sift through all of the different tags, and I actually had quite a few inconsistencies - to my horror!
I also had AlbumSort, which I forgot about, and also SoloistSort! But they are no more.
I'll keep you posted of other news . . .
Regards,
Paul
. . . 'ya know, I think the reason why I was having issues last night was simply because I had not performed a RESTART after installing mp3tag s/w! Upon booting-up this afternoon I seem to be able to perform actions such as removing any/all tags, as well as deleting unwanted characters.
Great to hear that this has been solved for you. Happy tagging!
Hi Motley,
Many thanks.
I still have a good deal of edits to make though. I need to replace lots of artworks . . .
Paul