Yeah I understand, this is a very critial info I was not aware.
I guess fast/easy ways to avoid this problem exist.
I mean, since I already could have tracks from my library with different tga versions than ID3V2.3 (APE & others).
How I detect these files?
If they are abig amount of files, how you delete the APE tag version keeping ID3V2.3 tag version metadata?
& how you keep the good APE metada? How you convert to ID3V2.3 the APE metadata you are interested in?
If you don't care about the content of the APE tags and just want to get rid of them, it's quite simple. In the tag options, select only APE for Remove, select all loaded files, and click File -> Remove tag or use the keyboard shortcut CTRL+R.
If you're hesitant about removing the APE tags without checking them, your only option is to inspect them. You can make this easier by marking APE for reading and creating an export file. Simply enabling ID3v2 for reading and then exporting these tags can also be useful for comparison.
Exported files can also be imported again.
But exporting and importing is a broader topic, and if it really becomes urgent, it's better to create a new thread for it. Take a look at the documentation for export and the Convert->Textfile-Text function.
My example referred to APE tags, which exist in addition to the tags in ID3v2. It's also possible that different content exists for one and the same tag field in the same existing tag field. This makes it clear that you won't get any further without visual inspection.
Even I have no idea APE exist & what it is for, I do not want incongruences between softwares & tag versions. I am almost sure I do not use APE tag version, but who kows (at least totally sure I do not use APE aware of it).
The following:
& this:
Means I need to first cheeck wich files use APE & then cheeck tracks one by one field by field (both steps manually).
I will keep the following to investigate in the future, if I detect more APE tag versions maybe is something I need to cheeck, but for the moment is 1 track from 36 thousand.
This has been added with Mp3tag v3.30a and is not available to the OP, who is using Mp3tag v3.01 on MacOS High Sierra 10.13.6 — an outdated and unsupported version of Mp3tag for Windows on Mac via Wine.