Sorry for the delayed reply - been quite a bust day and I haven't had the chance to catch up. Really appreciate the detail in your reply.
The wife is running Win 10 Home, while I'm running Win 10 Pro. I built my machine lean - no bloatware what-so-ever - not even the crap that comes with the hardware you buy. I told the tech to keep it lean - if it's not absolutely needed to run the hardware or some other reason - don't install it!!
I tried the portable version of calibre. No change. Still glitchy.
Then I rebooted in Windows Safe Mode. My whole desktop was messed up (proably the resolution setting) but playing with the installed version of calibre I found no issues. Seemed to save quickly when I added extra tags and saved them.
I did notice though that having the MDE open and clicking next repeatedly, any tag field that was empty, the software froze for a beat. This even happened in Safe Mode. Not sure what that means?
I have realised the issues all stem from a "write". That is, saving metadata, or updating an exising column or cell. I'm not sure what software I have that would effect that, or how I'm going to track it down.
If I recall correctly, Calibre was one of the first programs I installed, but I'm not sure if it was doing this then, as I just opened it, then moved on to the next piece of SW to install.
I am asssuming because all the calibre plugins showed in Win Safe Mode, that they aren't the problem, so not much point installing from scratch.
Check Library returned some results - mostly me taking a copy of the ebook and creating another version inside the library folders. Still, Calibre doesn't know thay are there unless I tell it.
So...any suggestions on how I can track this down?
Thanks