I had a weird new problem with tags/metadata, where the wrong track info appears when I play some tracks through JRiver from my NAS through my MUSIC COMPUTER (only about 100 tracks out of over 50,000), although I know the information is correct in the metadata. And the connection between the correct data and the incorrect data is weird - it's always another track I do have, but not at all connected - eg 'Academy of St Martin in the Fields Chamber Ensemble\Schubert Trout Quintet, Adagio and Rondo\Quintet D667 The Trout - Scherzo Presto Trio' shows as 'Marta Gomez\Cantos de Agua Dulce\Confesin'. So I'm reading Marta Gomez - Confensin, but hearing Schubert.
I eventually solved it - but I'll post my solution anyway in case it's useful to anyone else.
THE ISSUE: Recently some tracks (not all) show the incorrect metadata when playing through JRiver even though, when I check the metadata directly, it's correct. What's more, this isn't fixed by recopying the tracks from my master collection.
THE SOLUTION: I recently updated my NAS, and gave it a slightly longer network name (only 2 extra digits). As a result a few track file-path names became too long, and this was causing the problem. When I changed the file path (eg, reducing Academy of St Martin in the Fields to ASMF in the above example), it fixed the problem. So now, when I notice it, I make a note and shorten some part of the file-path of the offending track or album.