Offset contours and planar curves won't connect via boundary surface

I’m trying to create an offset surface for further processing. I create a series of contours, offset these, however something in the data management excludes a curve(s). The problem curves/surface can vary based on the offset parameter.

I could loft between the internal curves, then remove with Boolean but feel there is an easier solution. Seams simple but I can’t fix it via the data tree. The curves are planar too.



Contour & Surface Boundary.3dm (440.4 KB)
Contour & Surface (18.7 KB)

the green group is working right now but later you could try to find why the one in the red is not working.
also while working with tree it is better to realize not to use simplify at whole input/output.
Contour & Surface (15.8 KB)

Thanks, what do you think the problem is further upstream?