I won’t say it’s impossible but in general, Rhino can fail with shapes that taper to nothing. There can be zero volume or surface area at those points. I wrote this demo to show how it might fail but it works!
So I added a second set of control points, thinking it might create straight lines at the points, but it still works, so I guess there is hope.
Finally, on the subject of Member Index vs. Sort List, I wrote another demo to illustrate how Sort List works using the other input(s) that get sorted in the same sequence as the ‘K’ input.
The cyan group is a snippet of your code using Member Index. The white group shows how to use the extra input(s) of Sort List to get the same result. The yellow group culls zero length (invalid) lines before moving them 200 units in the Y direction.