I love this board! I'm still very much a Calibre rookie and there's a lot of great information here. I've left out a very important fact here that happens on EVERY metadata edit, without exception, so much so that it became background noise. Running Windows 10 by the way, and the library is on my Synology NAS, mapped as an M: Drive. The first save I try after editing metadata, I get this...
error (32, 'delete file', 'The process cannot access the file because it is being used by another process.')
Be gentle with me, I'm a rookie. But that might've been nice to tell you all at the beginning, eh?

Sometimes I get that error 2 or even 3 times before it finally lets me save the thing.