If you even run the game at 1080p while 120hz are enabled, if you ALT+TAB you'll reach the desktop, but the image will be frozen (yet you can still move the mouse but all actions takes tons of seconds to make effect, and you cannot ALT+TAB back to the game), forcing you to force reset your PC, possibly causing a repairing method activate on BIOS bootup

This should be something to be looked into for a possible future patchie/hotfix/whatever.

Windows 10 1909's latest version (No, not touching 2004) and all drivers up to date.

For me it was solved by disabling Windows Game mode

I'm currently facing the exact same issue, were you able to find a fix? I tried what was mentioned below but nothing worked.

Hello, Steam006 has updated his patch to 2.0.0 recently, removed DLLInjector.exe and most importantly, the ALT+TAB freeze problem seems to be solved. I tried it just before multiple times and haven't got my system freezing. I advise you to download and try the latest version, I hope this problem gets solved in your cases too.

Update: Unfortumately, the alt tab problem was solved in a different way than Steam006's 2.0.0 patch, because I tried alt tabbing right now with the patch installed and the system froze again. But still, using Steam006's fix without DLLInjector is worthwhile enough.