What is your computer case? I ask because you are using a U version of Noctua, and not a big D version.
It sounds like it's overheating. I mean, if I read your post correctly, while running memtest, your computer
1. runs at 80c just by running memtest.
2. after passing 4 passes, memtest push out an error.
The Noctua is the largest one for my 16 core Threadripper socket.
And is going to struggle to keep 16 cores coolish.
Memtest was run for only a single 2hour pass that was error free.
Yeah, I don't know at what temp the Threadripper starts to throttle.
Just hope I can get the air cooling to workout ok. 80c is not acceptable.
Cooling this is a work in progress...more fans/bigger fans.
What is your heating situation? I mean how many fans beside the cpu fan you have pulling air in and pushing air out?
tl;dr I suspect
1. overheating of mobo.
2. memory dimm died due to overheating
3. storage devices is dead/dying
In that order.
It is a full tower case that I'm still learning about how
much air flow it is going to need.
Default front 200mm and back 140 mm fans.
The Noctua heatsink is going to a 3000 rpm fan from the default 1500 rpm one.