Your file is working for me. What version of Rhino are you using? I’m using 7. If you’re using an earlier version, I suggest try recreating my def using those components instead.

Hi. The curves I am working on aren’t exactly on the XY Plane but kind of complicated. I have attached the GH file. There is some weird offset going on here when I used your method and the one posted above by Ethan.

Hi. The curves I am working on aren’t exactly on the XY Plane but kind of complicated. I have attached the GH file. There is some weird offset going on here when I used your method and the one posted above by Joseph Oster.

Well my goodness, who could have ever, ever, ever predicted that???

Since all your curves seem to still be planar but not the xy plane, the goal is to find the plane they lie in and then use the offset relative to that plane. I did it for the first curve. Hopefully, if this works for you, it can be adapted to the remainder.