ma_t14, this is not about mb changing any of the tags.
This started from the tracks not being in track# order. Not having found an option (I since was directed to where this option is located) to direct track # order (again, I didn't have this issue previously, with other albums, they automatically displayed according to track #), I went into the subfolder (not in mb) for that album, in a backup, and renamed each file, prefacing each name with side and track number. I hoped that this would force mb to properly order, plus make it easier to reference tracks when using the cover info.
I then deleted the folder from mb, hence from the computer storage (there is another thread about this issue, which you have seen), copied the folder from backup to storage and rescanned with mb. At first I thought that mb was simply re-adding the folder from some secret storage, because the track names still didn't reflect the name that I changed them to. Later I saw that I could separately list the track file names, which displayed correctly. But the track names are still different from the file names, missing the side and track # info. I don't see why mb is stripping the side and track # (eg A1, B2, or S1 2, S1 3) from the file names when it displays the track names. They should be the same. Unless mb has a cross-reference somewhere from previous scan, so is continually associating track names from that folder name with track numbers, regardless of file names. This is just a guess.
I know that I can bulk change detail info by highlighting all tracks then going into detail and entering data. But these changes were different for each track.