Windows 10: Regedit Not Responding during Export of All records

I have a Toshiba 64 bit laptop running Windows 10 Home Version 1703 (OS Build 15063.413). I wanted to see if I could figure out how to disable Cortana (it's a memory hog and I NEVER use it) and wanted to look through the Registry file. As I always do when opening the Registry, even if I am just looking at it, I always do a backup of the entire registry file, as a safety precaution. At least I thought it would be, till now.

When I did the Export to the usual folder, about 3 seconds into the export, a Not Responding message appeared in the title bar. It sat like that for about 10-12 seconds and then resumed. However, when I looked in File Explorer at the size of the backup file, it was almost double the size of the last one which was run on 7/9/17. So I ran the Export again, this time it ran seemingly with no problems. The size of this backup file was close to the one from 7/9/17.

Just out of curiosity, I ran the Export again and again it gave the Not Responding message. As with the previous one, it finally resumed and finished. The size of this file was again different from both of the previous ones and the one from 7/9/17. But this time it was smaller.

I ran the Export again three more times and only the last two were the same size. Now I wonder, how much credence do we give to the backup of the registry file? From this experience, I'd say it pretty hinky and probably not to be trusted.

Is there a way to get an accurate Export? One that can be trusted if it is needed? Does MS know about this problem, or care?

I included a screen shot showing the sizes of the registry file backups and I indicated in the names which were the result of Exports that had the Not Responding message.
Thanks for your help and suggestions.

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