Oh, yes, I have had that problem in spades. This is how I had to originally fix it:
https://www.mobileread.com/forums/sh...14&postcount=4
However, since then I manually reinstalled Windows 10 Version 1803 April 2018 Update by using the "Windows Media Creation Tool" route. I specified "keep user files and existing applications", then let it go.
I then manually downloaded the cumulative Version 1803 update for September 2018 from the Windows Update Catalog at
http://www.catalog.update.microsoft.com/Home.aspx and ran it.
Result: the Windows installer for 1803 treated the prior installation as "legacy", and totally reinstalled the Windows 10 user permissions and security settings, among all of the other things it does. That fixed it. No more Calibre temporary file errors, and just dying without notice.
DaltonST