having this problem in UE5.2 when I added a copy of MH groom hair that didnt have a LOD issue to a new blueprint character, then it started disappearing at distance.
I tried fiddling with every suggestion on here, then switching them back so I would not get lost too far down a rabbit-hole of random changes. In the end the machine hung and I had to restart it, and then it worked.
so if you are having problems after setting groom hair in a blueprint, maybe restart UE before you start changing too much.