My character's hair gone when drag too close

I create real time mocap character, with aMetahuman retargeting, and I add groom (All from blender)
The import was perfect, even retargeting, bind, bp.
But when I drag in viewport to character,hair was gone with some glitch.

Normally Groom problem cause from LOD, almost disappear when ho to far, but It’s opposite case.
There’s no camera, and It looks like not from LOD problem.
Even disappear distance too different every angle!
How can I solve? Does anyone help this newbie​:sob::sob::sob: