Hi Frank, thank you for your bug report! If you have the .3dm model file for that shape, can you please post that as well? It helps me a lot in tracking down bugs to have the actual model file for testing.

From the looks of it, that is a display mesh problem. The meshing done for display kind of takes some shortcuts in order to be fast, on some shapes with shallow curvature it can look sort of bad.

However, when you do an export to a polygon mesh file format like OBJ, the export mesher does a more careful (and slow) job of the meshing and is not likely to run into that same particular problem there.

- Michael