Did you find a solution?
I am having exactly the same problem
Tried all the same and more then that.
My pc I bought especially for Twinmotion:
RTX 3090 24gb
Ryzen 7 3700x
ssd 240 and Ssd 480
64 gb
850w gold (edit: just find it’s a 750w)
I can not get the same problem with all kind of test programs.. like Furmark.
Only with Twinmotion.
It’s a bit better when I use Afterburner and put the power slider down to 60%, but it still happens after a while or while rendering at higher samples.
The sample Lakehouse for example.. I can get it to show and render in the high RT in the viewer.. but when rendering it shuts down after a while..
black screen, and have to manual shut down the pc and then start again.
Temperatures are not the problem as far as I can see.. they stay below the marges.
The next thing I want to try now is, getting a new Power unit.
I did get the pc second hand, and maybe the power unit is a bit older than the rest, I don’t know.
Can that be a solution?
The other solutions I could find on this site I tried.. and I get a bit hopeless with this situation..
edit: just looked at the power unit and there’s a Corsair 750w instead of 850w they had told me..