0d Q-Code is killing my brain.

[DogOfRaw]

Hello All,

First post here, I'm hoping for help with an issue that has me chasing my tail in a major way.
So I rebuilt my PC in late 2020, here is the spec:

CPU: Ryzen 7 3800x
MOBO: ASUS ROG STRIX x570-e
Cooler: Cooler Master Hyper 212 EVO
RAM: 2x8gb Corsair Vengeance LPX DDR4 3600mhz (4x DIMMs for 32gb total)
SSD: Corsair MP600 NVMe 1TB
PSU: Aurium Pro 850w
GPU: Pallit GTX 1070

OS: Win10 64

 

This build ran with no issues for two years.

I recently moved country, and brought my PC via checked luggage. It was well packed, and arrived with no visible damage - it booted fine after I got it set up.

But after running for maybe an hour, it blue-screened on me, and refused to boot again. When I opened the case the mobo was displaying a 0d error on the q-code display.

After a few failed attempts to boot the system, I breadboarded it so I could try isolate the fault.

I followed some advice from google and slackened off the screws holding my CPU cooler down, to remove any strain on the mobo they might have been causing.
The power in my new house is not the best, the lights will dim periodically, so I suspected that the PSU my not be outputting a stable voltage. I hooked the system up to a filtered UPS and probed the PSU outputs with a multimeter but all appears nominal.
Next I tried the RAM. I was able to boot the system with 1 DIMM in the A2 slot, and with 2 DIMMs in A2 and B2. I even got it to boot with 3 DIMMs, but it bluescreened quite quickly and then gave a 0d when I tried to reboot.
I numbered each RAM stick, and have tried every permutation of placements possible, but could not associate the fault to any one stick. I've run memtest86 on all the sticks as well, but detected no faults.
In cases where I got the error with 1 or 2 sticks installed, removing the mobo coin cell and shorting the CMOS jumper normally helped.
I also updated the BIOS to the latest version but that didn't seem to change anything.
Over the course of this testing the issue seemed to get worse. Sometimes the mobo would start to power up, but a second or two after the relay in the PSU had closed it would power off again. It would then try to power on by itself (no button pressed), with the PSU relay opening and closing several times before I would turn off the PSU switch.
After being left overnight this behavior would normally disappear.

I followed my hunch at this point that it was a mobo fault, so purchased a new ROG Crosshair VIII HERO.
I rebuilt the system with the new mobo, and to my dismay I am seeing the same fault again! Same 0d error code and all.
I am looking for any ideas on what to try next, before I go whole hog and order a new CPU, RAM and PSU (might as well get a case at that point and build the PC of Theseus from the leftovers haha).

TLDR: getting a 0d code on two mobos, can't find any RAM faults, any way to see if it is the CPU or PSU?

Thanks!