Problem with Case Conversion of Filename (tag is ok)

[astrohip]

Thanks for the replies. I'm fairly certain it is NOT an Mp3tag issue, since I can't change it directly in Explorer via F2. It's not a NAS. Not read protected.

BINGO! The answer is in the reply in that thread you linked, from JJ_Johnson. This is a Windows bug, going back at least ten years+. I'll cut & paste for future reference...

@JJ_Johnson

limitation of Windows due to it using a case-insensitive file system. If you just attempt to change the case of the name, Windows thinks the new name is the same as the old one. For example of this, open Windows Explorer and browse to a local folder, then try to change the case of a letter in a filename. It won't stick. You have to change the name somehow first.