Hi again @cgace!
I personally haven’t encountered this issue, and am having difficulty replicating it on my end. However, I have a few ideas of what could be happening here.
This thread seems to describe the same problem you are encountering, and you mentioned having adjusted some hair cvars, which makes me hopeful the solution from the thread may also help you: Weird Hair Groom Camera Shadowing Artifacts/Glitch - #4 by Adithya15
If this doesn’t work, I’m wondering if it may be your light itself. Rect lights and point lights start to display some pretty bad banding at large attenuation radiuses, though admittedly normally this problem is visible on shadows, not just certain shaders, and your radius has to be extremely high before this error occurs. Still, if the above solution doesn’t work, you may be able to narrow down the cause by playing with your light source. This may help you determine if the problem is indeed in the hair shader or rather something in the light itself.