I recently had a problem with the .obj export from rhino 6 to 3ds max.
Some of the meshes seem to connect the faces in a wrong way in 3ds max.
As soon as I switch back to rhino 5 everything works fine.
and it is best to set the obj importer options regarding normals in max to ‘faceted’ and smooth manually - there is an old bug in max that can result in corrupted mesh data, not directly visible but errors may emerge over time… e.g. normals smoothing / groups will not work as expected.