Just an update,
Fistly to respond to Mushioni, taht was my initial thought, but after running several run thought PSU Checker incloding adding LED’s and fans and AIO pump etc, it still runs under total 650w , and the gguidense from that site recommended a 750w fot the 80% rule. as mentioned, i have ran with a RM850x and the issue persists. i dont have/afford a 1000w PSU just to test this unfortunately.
Upon reviewing the system event log. Just before my crashes i see this error.
“The description for Event ID 14 from source nvlddmkm cannot be found.”
it seams to me this is a common problem among other users of AMD and Nvidia