At my wits end! PC Started to Freeze/BSOD! Puzzler

Hi,
Here's the specs:

• ASUS ROG Rampage V Edition 10
• Intel 5960X w/ Corsair H105 AIO & Noctua Fans x2
  
• Corsair 16G x8
• GTX 1080TI MSI SeaHawk x2
  
• Corsair RM1000X PSU
• OS is Windows 7 Pro

The system was running rock solid stable up to around a month ago. The CPU was modestly overclocked to 4.2GHz by only changing the VCore to 1.3V. The RAM was XMP 3200 profile that it was designed for. Nothing else was overclocked or modded in any way.

Games and programs started crashing randomly, so I suspected RAM. I removed each of the sticks and tested them individually with MemTest 86+. The testing process itself was quite odd. On various passes the RAM would either test all OK or have some errors with no particular pattern. But eventually I was getting a reproducible error with 1 stick of RAM (the other sticks all tested OK). So that RAM is now shipped off to Corsair for RMA. The remaining sticks of RAM have all tested good. Currently there's 4x16G sticks inside.

Then the PC started crashing again (BSOD with Error 0x124). A bit of googling seems to imply that that error is most likely to do with overclocking. So I reset all the settings in the BIOS to Auto, with the CPU running at the stock 3GHz and Turbo to 3.5GHz. RAM is now on 2133MHz.

And the PC still continues to crash, especially with Prime95 or ROG Benchmark. The temperature monitor doesn't show the CPU running hot (only gets to around 50c or so). If I go with 4.2GHz at VCore 1.3V it's an instant crash every time. If I leave it at stock 3GHz with Turbo to 3.5GHz, then it maybe crashes 50% of the time. Sometimes it BSOD 0x124 and sometimes the PC just freezes. It doesn't seem to crash when I max out the CPU doing other tasks, Eg. compressing with 7 Zip. Only occasionally with games and almost always with the benchmarking tools.

Nothing else about the hardware has changed in anyway. No recent major updates to drivers or windows.

Any thoughts? Could a faulty RAM stick have caused all this mess? Or is it more likely to be CPU (or something else) and has caused the RAM stick to be faulty? Or is it something else completely all together?

Seems to me like CPU may have been damaged. Always a good idea to try reinstalling CPU and replacing thermal paste.

Second the above, that was my first thought.
The other thing that comes to mind is a chip on the mobo getting hot due to lack of cooling but may now be damaged.
You may need to pull the heatsinks to verify.

I suggest resetting the cmos before checking anything, see if that helps.

Could be a faulty PSU, where fluctuating voltages have physically killed a ram stick sat on a subsequently dodgy link to the CPU.

So try another PSU if you can.

BSOD 0x124 is most definitely CPU voltage related. When overclocking, it directly means increase Vcore to get stable.

But I would suspect it's the mobo at fault if not the PSU. CPUs don't die like that from my experience. Not without extreme voltage and temperature and even then it's gradual.

Since writing I've found that the issue is that CPU, which I've RMA'ed with Intel. Swapped it out with a 6800K from a friend's PC and everything worked sweet. Thanks for your help!