iTunes on my Windows 10 PC reverts back to default location after I change it

For well over a decade, I have stored my iTunes media on a second 3 TB internal hard drive. Sometime last year my iTunes glitched and now, whenever I close and reopen iTunes, everything goes to the default iTunes folder in the Music folder. No matter how many times I change it, it always reverts back. I thought it might be because I was still using Windows 7 (yeah, I said it) but I just bought a new Windows 10 computer with an 8 TB secondary internal hard drive and was going to start from scratch to clean up my library but it is doing the same thing. This is extremely frustrating. Is there some kind of fix for this?

[Re-Titled by Moderator]