Crashing To Black Screen - PC Locks Up

Midgame to late game, the game is crashing to black screen and  PC is totally locked. Control alt delete, etc. does nothing. Sound is stuck, etc. Rebooting PC and re-entering game quickly often will place me back in spot but immediate crashes to black screen and locks PC again.

This has been happening approximately since last update. I've repaired game files multiple times, updated GPU drivers, etc. I'm runnning Intel 12900 CPU, RTX 3800ti, 64 gig DR4, Win 11.

One note that may be telling: Before the crash, the game is running 144 FPS, after crash, always 22 - 44 FPS. Only reloading GPU drivers returns fast FPS. (I have done a clean reinstall of video drivers). 

Running temps are mild: CPU max - 150F, GPU - 155F.

I am so frustrated, I'm ready to uninstall this game I've invested nearly 2K hours playing : (

Any suggestions are most appreciated.

Thanks,

Bob