Hi Steve, it's probably hard to tell whether the problem is in the STEP format handler itself, or if it is a NURBS tessellation problem.

That's a rather strange looking artifact, but it kind of looks like some kind of polygonal patterns, that may be more of a tessellator thing.

In that about box screenshot, it mentions OpenCascade, that's probably what is used for importing STEP and tessellating to triangles as well.

- Michael