Hi,
The error message “Insufficient interpolation points” means you have a list of only one point. But why this would happen, as you plugged three distinct wires in the same input ?..
As discussed here, this is a tree structure problem, your items are in different branches and therefore not considered as a single list with three elements. I STRONGLY recommand using Merge component to anticipate - and correct with Simplify or Flatten - these problems.
In order to repeat this process on all your curves, you need to regroup all your points by lists of 3 elements, which means a tree with several branches, which means : graft.
Interpolation issues.gh (12.9 KB)