Hi Martin,
This is very strange but my issue seems to have gone away. Apologies for taking so long to reply, but I've been trying to replicate again.
I have 3 computers running Windows 10, 1 Pro, 2 Home. When I first had the issue on my Pro machine, I tried on the other 2 straight away receiving the same result failing about 16% etc. Then I saw in the forum about switching off the shields, this took the issue to 25%-30% respectively. I received the same issue on the other machines. I then tried the repair on my Pro machine only, as per RockSteady's request, of course rebooting after the repair. Same issue of failing when rerunning.
After you posted, I tried again to generate a rescue disk on my Pro machine to get the logging details, and to my surprise it worked. I tried the iso, that worked too. Weird.
So I tried on the other 2 machines, they worked too. Shields on, all potentially affecting programs running as well.
I checked my Windows update, no patches only a couple of updates of Windows Defender.
Do you want to close this off pending recurrence?
Kind regards
Paul.