So I recently had some trouble with a two year old 5950X and ended up sending it out for warranty and it was replaced by AMD. I have been tinkering with the new cpu and I'm trying to get an undervolt completely stable. Things are not too bad, I can run prime95 for hours with no issues and the one hour OCCT stress test completes with no problems either. However, almost every night when the system is idle it crashes and restarts with no BSOD. The event viewer shows a WHEA error for apic ID 0 or core 0 and that is my best core according to Ryzen Master. Currently in the bios and the curve optimizer I have core 0 set to negative 1 offset. It was P95 and OCCT stable at negative 5 but whenever it crashes I go into the bios and adjust the curve by 1 or 2.

If I am able to pass P95 and OCCT why is this single core having issues and causing crashes only at idle? Aside from just waiting for it to crash again is there any other testing I should try?

Thanks!