Is the artifact baked into the normal or diffuse maps? If not, try turning off "import tangents" when you import the mesh. I know epic says otherwise, but it ruins mirrored normals.
Here's what the mesh looks like when I imported from maya. There's no diffuse or normal map on the mesh but everything looks as expected. I do not see any visible artifacts other than the hard edges on the interior of the window (which were also present in the OBJ). Are you exporting from max or maya? Are you positive the…