Hey, sorry for the late reply. I never figured that one out. I have heard that it is a specific bug within UE5. I tried to ask when they were going to look into it, and I never got a reply back. I think right now there is a shadow option on the hair (can’t remember which) that made things a little better, but not perfect. Also, the crappier answer is, you have to light the scene differently. That sucks though.
I think I’m remembering one other work around that had to do with getting rid of any emissive materials in the level. That seemed to help according to another post that I found at the time. I never tried it though, because my scene was on a spaceship and there were emissive materials everywhere.
I hope you have some luck with this one. Maybe Epic can come up with a fix…HINT HINT! lol.