[Help][2.80]Some vertex groups won't be exported

I am trying to create a character model for Daz3D.
Daz generates bones from vertex groups of obj file, so I have Mixamo rig a model then export it as an obj with vertex groups in Blender.
But exported obj doesn’t have some groups.
Why does that happen?
How can I solve that?
Thanks.
Untitled (1).fbx (1.0 MB)