ClosedSweep Issue - Rhino.Geometry

Hi, I am trying to perform a sweep one rail on a closed curve, which is a boundary curve of a polysurface (brep).
All works well except when i try to perform a closed sweep with sweep.ClosedSweep=True.
I think it might depend on the fact that the input curves (sections) must be more than the 4 points I am using, depending on the number of curve composing the rail curve.
here a screenshot in case you can spot something strange.


so this is the gh, I actaully tried to change the profile curve (to get a profile curve with the same number of vertex as the number of sections) and it gets no substantial improvement. the Boolean value of the closed sweep doesn’t work on True. Any ideas?
Fsweep (5.1 KB)

apparently this was already discussed here,

maybe I should post this in the old post.