I've been working with my library, which is about 15,000 tracks; a mix of MP3 and other stuff. Much of my CD collection was ripped with iTunes v6, which seems to be where the problems began, though as I say, this is still a mystery to me.
Here are the oddly mixed results I get:
MP3Tag reports (!BAD ID3v2), and no info is displayed for the tracks.
MediaMonkey likewise cannot read the track information
MP3Diags reports some detailed information, possibly most relevant: "ID3V2.3.0 tag containing a frame with an invalid name: blah blah blah."
iTunes v11 is unable to read the track info (created by iTunes v6). I no longer have iTunes v6.
Windows File Explorer reads the file info and displays all expected details.
WinAmp is able to read and display the file info.
If I select some tracks in File Explorer, go to details, and change the rating of the tracks (stars) a couple of times, it rewrites the tag, and then all the above-named programs are fine with the tracks. This is not really a viable solution, though, for 15,000 tracks, as I have to navigate each folder separately.
Why can Explorer read these invalid tags, but none of the purpose-built programs (including MP3Tag) can? I'm befuddled. Will be happy to provide further data. Thank you, experts!