About import skinned mesh from maya to unity

I have a skinned mesh(no animation, all joints set scale compensate set to false) in maya, have exported to fbx to import in Unity.

But it seems some faces are gone.

As shown in attached images.

Anyone know how to fix this?

Thanks.

 

Nobody knows or ever encountered this issue?

 

Just a thought. Have you checked your normals?

 

Hi, thanks for reply.
I have double check normal, and tried to set unity import setting to calculate, but the problem remains.

Thanks,

 

So one thing is that my joint have no animation attached, will unity be ok to this situation?