Exported polyline (stp, dxf) lacks control points when opened in Inventor

I need to send drawings to a fabricator who’s using Autodesk Inventor and apparently when he’s importing my files (we tried stp, dxf, dwg and Rhino v5 files) he gets a line without any control points.
My lines are filleted polylines, that is straight segments and curves and he needs to be able to select the different parts.
Any hints on to export things differently? They seem fine to me when I re-import them in Rhino.

b1_v5.3dm (26.2 KB)
b1.stp (9.1 KB)

You might want to check your DXF export options. There are settings to accommodate most downstream programs, for example if the fabricator wants separate lines and circles I would do something like this:

You can also export polylines as line segments if that is what is wanted:

Thanks a lot! I’ll try those options…