Seems there is a big gap !
So something is not right
You are not obliged to put the "section" at the beginning of the curve line
It can be anywhere, when you make the sweep, you can pick a "profil" and then the rail
the profil will be automatically perpendicular for make sweeping!
maybe this can help you to select the good rail :)

Ps but one more time it's more easy to answer when you post the 3dm zipped!