There is an oddity in bgs nif exporter. If the Pivot point of the mesh is far from the actual mesh, distortions occur during export. For meshes of the body, face, hands, it is appropriate to use 0,0,0... For further work in os. But... The more polygons and the further the mesh is from 0,0,0, the more deformations. You should also know... The actual coordinates 0,0,0 os and 0,0,0 3ds are not the same. There is a microscopic displacement.