Exported rigged geometry weirdly distorted, looks eaten away

I’m having a strange problem of certain bones in my rig causing a weird distortion when exported to .fbx and imported into Unity. Basically, the problem bones are causing the mesh to look eaten away: 

Note the cheek area where it looks punched in instead of being smooth. I’ve done many tests, but can’t figure out what’s happening. All the other bones are fine except for 3 problem bones.

File attached. The problem bones should be selected.


RigDistortionProblem.blend (5.32 MB)