The fourth of the three possible issues is that the DWG comes from a special version of AutoCad (AutoCad Architecture, AutoCad Civil…) that uses special objects. These cannot be imported to any non-Autodesk application. The originating applications have an “Export to AutoCad”-type function that converts and exports these special objects into standard AutoCad drawing elements.
ah interesting, thank you, I wasn’t even able to get to that stage. The model is supposed to be in 3D, so maybe the file is corrupt in some way, the dwg originally before I got Pro was about 20,000KB