Nice to learn you solved the problem. I got recently hard freeze problems similar to yours.
During flights, it happened frequently that images froze suddenly for a few seconds, and came back to normal.
However, few minutes after normally closing MSFS the PC screen suddenly went black like entering sleep mode, no mouse, no keyboard, had do do a hard reset by long pressing power button.
The event viewer reported a NVIDIA driver error, followed by a windows error.
I realized that stressing my graphics card with monitoring software like OCCT caused the same freezing symptoms and error messages, short time after closing OCCT, so I eliminated a MSFS 2020 software issue.
I changed the graphics card and problem is gone. I suspect this is due to GPU chip aging resulting in internal timing faults and driver reset. Driver reset didnāt crash the game, but caused subsequent windows freezing. I didnāt try here but a proven remedy for such issues is undercloking the boost GPU clock (for example 5%). My card was only 2 years old, and I never overclocked it, nor increased the supply voltage, but it was a little bit factory overclocked. I believe the initial clock frequency margin was unsufficient for stable operation after die aging.
I just had it last night, But I was streaming simultaneously. Flying the A310 into Istanbul, about 500 feet before landing, the SIm froze, and my windows 11 froze. And yet I was still streaming and also my webcam and mic were still workings I can see that on stream/
Around 1min to 2mins later OBS started going wild with RED information as the system unfroze itself and then OBS disconnected itself and stopped. Then after the sim is unfrozen and landed as normal, but when taxing itās strutting 
And thatās on low to medium - maybe 1660TI is overkilling it
I seem to have hit a ārich seamā of complete PC hangs in about 1 in 6 flights.
Just happened again, about 5 minutes ago, and this was flying the 414AW, not even the likes of the PMDG or Fenix 
Finishing up a KJAX/KATL and I was parking up, just spooling down the twin engines andā¦.
At least this time a few minutes of waiting aghast, the PC restarted itself.
Iāve usually had to do a hard switch-off.
Maybe SU12 will see an improvement. But Iām losing interest in simming at this rate.