For loft or sweep, curves all need to have the same direction, with start/end points aligned. The Flip Curve component will swap directions if necessary so that all input curves match the guide curve.
As to the height problem, see this:
This (below) adds just one more section curve in the middle and moves the others around a little bit,
20191030_Sweep2_problem_2019Nov1a.gh (20.8 KB)