Actually it does not crash
due to 6Dof/TIR Enabled.
That crash is just the final result of something that went wrong before.
As for the cause of this, initially you've mentioned that you got a new PC.
I take it that the same BAT installation went well on the old one, so for the time being, the new PC is suspicious.
Even more so since you said that sometimes the game works well and sometimes it doesn't. That's unusual for IL-2, usually it either works or it doesn't, but not both randomly.
You could try and see whether Stock IL-2 works for you.
You could as well try and see whether causing stress to your PC's hardware raises issues.
For CPU stress test you can use Prime95 (
https://www.mersenne.org/download/). It needs no installation. Leave everything at defaults and let Prime95 run
for a couple of hours and check back whether it reports any error.
For the GPU, use FurMark:
https://geeks3d.com/furmark/Let it run in full screen at your monitor's native resolution for half an hour at least and see whether your PC survives that stunt.
Mike