Solved Crashes, Crashes, Crashes, and weirdness

OS : Windows 11 Home Edition
MB : ASUS TUF Gaming B550 + WiFi
CPU : Ryzen 5 3600, then Ryzen 7 5800X
AIO MSI Watercooling
SSD : Samsung Pro 980 M2
RAM : Corsair Vebgeabce Pro RGB (2x8)
GPU : ZOTAC 3070 Ti Amp Holo
PSU : 650W Gold 80+
VR : Oculus Quest 2

Hi all,

After 2 years of flawless service, my computer started to crash in different ways while gaming, mostly in VR.
Some games, like Assetto Corsa Competizione, would crash in under half a second after launching a session.
Other, like Automobilista 2, would hold for 10/15 minutes before crashing.
A few "lighter" games, such as Rez Infinte, would not crash.
I've also had crashes in non VR games (Two Point Campus and others.)
It turns out that one of the cores of my Ryzen 5 3600 was severely overheating under stress (96 degress while the other 6 wouldn't reach 40.)
A that point in time, it seemed like it was a faulty temp sensor that was the culprit, showing a temp over 100 degress hence inducing shutdwon. How could one core overheat so dramatically and not affect its neighbors?

But...

As the Ryzen 5 was being replaced by the Ryzen 7, it turned out that the cooling paste had turned into a chewing gum like substance, indicating that there was overhating indeed.

Initially, the new CPU changed nothing. Crashes would appear at the same rate, in spite of the temperature of every core being nominal.

The real weirdness starts here : after a clean install of W11 (GPU drivers + Steam installed + Oculus Software), the first day wasn't so good. More crashes.

But on the second day, everything was flawless. No crashes in spite of several hours of VR gaming.

On the third day... It's the worst it's ever been. For instance, I can't even get past the menus in Assetto Corsa Competizione. A flahing blue screen before the main menu, and reboot.

I've done everything I could, all the way up to updating the BIOS. No dice.

I previously thought my GPU was at fault. The repair guy found that overhating core, which I never diagnosed, as I never thought such an issue was possible and only checked CPU package temp.

But since crashes now happen outside of gaming, I'm thinking it's anything but.

Sorry for the long post, but the weirdness of the situation has engulfed me.

Thoughts?

Cheers.

Thanks for the replies. I shall disable XMP later and let you know how it turnedout.
I would however dispute the idea that I need a 750W PSU. Maybe it's the case now with a more powerful CPU (65W->105W), but with the Ryzen 5, my multimeter plug was telling me I would never get past around 500W. Makes sense as my 3070 TI pulls 315W at full blast, add 65W for the CPU.
Add whatever the rest needs, and I believe I end up well within the range of my PSU.

Am I missing something?

Balanced mode enabled, XMP disabled. No Change.
What's more, my mechanical hard drive is no longer detected. That has never happened before.
I am at a complete loss.

I'll take my PC to the repair shop on tuesday with a new MoBo.
I've sort of given up on trying to fix anything at this point.
Would you all be interested in hearing how it turns out? MoBo replacement was the tech's idea.

Thank you very much for that, I can return my MoBo if it turns out it's not the solution.
But regarding the PSU, 2 quick things :
- I've tried with one screen unplugged, no effect.
- I downgraded my GPU to get 70% power max (capping at 210W instead of 315W), no effect.

As for the RAM, I'm surprised to find out the speed was incorrect. Thanks for pointing it out, I'll set it at a fixed 3.2GHz.

Quick upate : after re-enabling XMP, my computer is again able to go trhough benchmarks (3DMark stress test passed without issue with very nice temps.)
I plugged it in a separate outlet, one screen on. My multimeter plug tells me it caps at 475W.

Does it mean my PSU is limited to this value? (650-12% equals 472W). GPU runs at 100% @ 73 degrees (Throttling temp is factory set at 83.)

CPu runs at 71-74, but the load is low (20%). I yet have to find a benchmark that stress both at 100%.
Any tips?

Thank you so much again.
Very interesting to know that a multimeter is no reliable way to test a PSU, I would never have guessed.
I would however like to point out that my PSU is not a cheap no-name one. I simply do not remember the brand, but I was careful to buy a proper one. I believe it's a Corsair. (Gold cerifaction).

But you all have convienced me that I need a new one. After all, I had no issues before adding another screen (but the problems didn't start right away, it took a couple of weeks.)

I'm currently browsing to check whch one to get. I've settled on 850W.

I'll let you know how it turns out once it's installed.

P.S : the missing hard drive was simply due to me screwing something up in the BIOS after upgrading it. It instructed me to do something regard'ing RAID which I did not quite understand. But it's back on and works fine.

P.P.S : just finished a 2 hour gaming session in VR with nothing going wrong at all. One screen off, nothing more.

And my PSU is a COOLER MASTER MWE BRONZE 650W V2 - 230V 80+BRONZE. 2 years old.
I now realize that C Master doens't have the best reputation, and that Bronze certif might not be enough.

I settled on a MSI MPG A850G PCIE5 Gold, ranked Tier 1 in the classification provided by phillpower2.

I feel pretty confident that it'll do the trick and make my system stable again (although everything has been fine for the past 48h). Many thanks to all, see you next for the final report.