Perhaps I was too quick saying its not ram.
Can be "fixed" by upping the voltage on the ram in bios.
its a power thing but i don't know if its the PSU or just not enough power going to ram.
OK, so after you said that, I decided to do another thing that, in retrospect, I probably should have done first of all, which was reseting my BIOS to default settings.
It hadn't occurred to me to do that because I didn't really change anything, the only thing I did was turning XMP off and on when I was testing if it was the culprit of the crashes.
Alas, when I tried to save and exit, the BIOS warned me that a bunch of stuff was changed, including the RAM voltage that was set to 1,35V and now is on "auto". So maybe when I changed the XMP settings it set some settings manually?
Either way, HWinfo is showing me the RAM is working at 3200MHz, which means XMP is enabled, so the default BIOS settings have it active. So I can't understand why turning it on by itself set those settings to determinate values (the frequency and timings were also set to specific numbers and now are all on "auto").
The good news is that putting everything on "auto" solved the Prime 95 stress test problem. It's been running for about 10 minutes and showed no errors neither crashed the system, and that's like, at least 10 minutes more than it was working before.
So I'm assuming I was having some weird errors that were driver-related and when testing to see if the RAM was at fault I somehow made everything worse. Cool.
Now we test again.