I know loft is a little finicky in general, and I have learned to iterate on loft problems by making sure curves are all in the same direction, sorted correctly, seams are aligned, making sure either no or all curves are kinky, and then adjusting the number of input curves until it works.

But I’ve got this file that is just not cooperating, and the problem does not disappear with any reasonable number of input curves.

Curves look normal:

…but the resulting surface has an unpleasant twist:

Here’s a very simplified file with the data internalised:

loft-problem.gh (269.6 KB)

Any ideas of how to solve this in a general way?