Hi there,
I am having the same problems with my Asus TUF RX 6950XT OC.
SC ( 3.22.1 - problems began with 3.20 afaik ) starts, running around for 10 to 60 Minutes. Sometimes less. Then all stuck, blackout and crash to desktop.
I have logged everything and saw the power consumption spike up short before the crash. So, like you, I ramped up my pwr supply from 850W to 1,2kW. But still the same problem.
I was advised that Adrenalin and all the small tweaks might glitch here and result in the ctd, Now I got rid of adrenaline suite and went to pure driver. Short Tests were more or less the same, I guess I was just lucky when I had almost 2 hrs of Gameplay but still ctd.
To get back control of my fans I installed MSI Afterburner. And now I will test some undervolting, since I guess the spikes are the problem (ppl say that the mobi glas does that - I could not verify this), and maybe this might take them away. But still testing.
Did you have any luck at all since then?
Maybe we can collect some stuff we all tried and combine them to work on a solution.
I lost enough aUEC for the moment .. *sadface*
EDIT: **bleep** .. just realized you answered your own thread - Undervolting it is then. Do you have any numbers that I might test? Or did you really just hit auto undervolting?