Strange, but driver 440 seems to fix FH5 crash issue.
I only saw driver 440 fixed ACC cpu loading issue in it's release note, but some people talking about this driver fixed FH5. So I gave it a try. I tested the crach issue by switcing cars, it usually crashes about switching 3~5 cars. But using driver 440, I siwtched 10+ cars and over 1 hour driving, the game didn't crash.
Maybe you can try it.