I get this problem a lot when exporting from iClone to Blender using the Datalink plug: some vertices are way out of place and deform the mesh, and they are also not moving with the animation. For in place animations I fix it by just moving the vertices but when it’s moving there’s no way to fix it.
I only have this problem using the datalink, normal exports work fine.
Oh and it seems to not apply to cc3+ characters, but I’m not entirely sure.