To make life easy I put a copy of the db into my dropbox at this link:
https://www.dropbox.com/s/0hgdsmw60r...tadata.db?dl=0
Just to be clear I am
not running calibre from Dropbox. I just put a copy of the file there so you could see it. I run Calibre from an external hard drive that I move from home to work and back.
ETA: I also tried uploading one of the books from the affected library to an unaffected one and there was no issue with the tags overlapping. I'm wondering if I should just try creating the library again?