Nealx01
yea thats a valid concern.. its a bummer you dont have another set of ddr4 that you can toss in to see if the issues persist. 

i have a 9900k.. 9900KS z390dark and the exact same memory kit your using here. i would offer to throw them all onto my testbench but im not sure it will do much to help. you said you had that kit running at XMP since around xmas time. so we know the dark CAN run those memory ICs.. just that there is some issue with your specific parts. so me trying to reproduce an issue might not be of any help. 
maybe try to track down a friend with some ddr4 you can borrow for a day or 2 or even better test your kit on their system if possible. if you can run stress tests for as long as possible to see if you can get any irregularities. if your kit is at fault Micron has amazing support for waranty and RMAs also. i just had a faulty SSD replaced and it came today by coincidence. process was extremely consumer friendly. no hoops to jump thru and no silly policies  
let me know if you would like me to throw all the same parts you have together and see what my results are. i might be able to do it tmro if you can get back to me quick enough.

other thought, did you possibly move switch the bios by accident? probably not, but something to check in case you overlooked it. 

Thanks. It feels like I slowly have to RMA every single part of my system. Because I just can't seem to track down what's going on. And absolutely, the system ran absolutely fine. Pushed maybe not to the limits but I had months and months where there were no issues. System was going full speed ahead all the time, no hiccups.

Just noticed CPU Die Temperature shows 51C. That's the first time I see that as well. Never been that high in BIOS.

Every single time I restart I get a new bluescreen:
CRITICAL_PROCESS_DIED
the
ATTEMPTED_WRITE_TO_READONLY_MEMORY

No way around it. Motherboard back in same condition with both CPU's. No boot like in the beginning when problem first appeared (GPU death). It's like riding down a hill with a flat tire, you'll get to the bottom but not in one piece(can't find a better way to describe it). Seems like I have to start an RMA today...

Well thats really unfortunate. To be captain obvious here... the bios stress test is total trash .and they are with every board from almosy every brand. asus has the only decent AI overclocking software. Its genuinely pretty decent.
I consider the evga bios stress test totally useless.
Those errors aren't actually that helpful in figuring out exactly went wrong. They are basicly some of the dozen or so errors that are really common with unstable overclocks.
Altho I've never actually seen the critical process one or read/write error. Those sound more abnormal
It sounds like your at about whits end. Maybe sending in the board is the best course. Just don't expect the bios stress test to be of any use period. Its totally irrelevant. Of course it's still possible the issues persist after you get a new board or yours repaired. Its still possible your ram kit is at fault. It appears you don't have a good way to determine if that's at fault or not.

Almost lost my mind... when you get into the Bios and open the first page you have the multiplier and such.

There's a voltage setting and that was showing 1.559 (I took a picture of it where everything is at auto and the voltage is that to the left, right after CMOS reset)

So I assume the voltage was set to that at start by the motherboard (?) and caused the CATERR crash when CPU voltage went up right before crash(?).

That would also explain why the 'CPU Die Temperature' was showing 51-53 degrees in bios. That's extreme with no load at all, no? CLC 360 was not the problem.

Just guessing though.

It's a shame really, thought I could maybe keep myself and of course EVGA from havig to deal with another RMA.

I might be able to test before sending the board for RMA, it usually takes a day or two for the RMA to get approved. I'll report/update here if I got the chance to.

CPU die temp isn't the same as CPU IHS temp, it can have a large variance. My IHS temp will max out around 40C but I can see the CPU die temp go up to 80-100C for a second or two and normalize back to 40C depending on what i'm doing.
 
In my opinion, most things are pointing towards the motherboard... RMA's take quite some time to process, like 3-6 weeks for motherboards.