Encouraged by the fact the fault diagnosis agree with my view and that of many here, I was pleased to get it back.
In the bios, I have to disable TPM and enabled PXE boot as the first boot option... Having ordered a few Ultranote IVs I know this is not the default config. I was therefore surprised to find my laptop with freshly replaced motherboard having PXE and TPM set as I left it...
Anyway, I pressed on and deployed my automated build to it.. left it doing nothing and within 30 hours it had the same issue again, multiple times.
I then grabbed a windows 10 1709 ISO, all the drivers on the pc specialist website and the oldest driver I could find (just the driver, not the full proset) and let it be. Survived most of friday but in the evening... back to square one...
View attachment 12153
I may have budget to replace a couple more laptops, but clearly don't want to give business to pcspecialist till this is resolved.
In fairness is possible they copied or even backed up your bios settings. I used to note any unusual (ie not default) settings when I used to do repairs and set new motherboards the same.
But... the fact that the fault remains isn't conducive to this line of thought.