Sweep1 incorrect

I can not get over this form using the “Sweep 1”. It seems that the section curves are not aligned properly.
Thanks for your help.
sweep1 problem.3dm (32.7 KB)

Maybe I’m wrong command?

from a CAD to another it is goes crazy!

if you split the S-Curve and use Sweep2 (choosing the square and circle as your rails) and repeat 3 times does that do what you want?

Because of the orientation of your rail curve, there isn’t enough implied control to determine the shape. Rhino has a bias for up and down relative to the Z CPlane direction that is causing the flipping.
You can either re-orient your curves so your rail does not cross vertical, or as an alternative use a 2-rail sweep instead.

Thanks John!