Curve offset issue

Im trying to create a rib structure and my plan is to generate cuts along the surface and offset them. Then create a surface out of the two curves and extrude the surface. Im having a problem though offset the curves. Most of them seem to work but I'm having an issue at the areas where the surface drops down. Its generating the top half of the offset correctly but the bottom half is flipped. Any ideas on how to fix the issue? Thanks