Sketch spline fails systematically

I have a spline which is already in my CAD model
I want to basically "smooth" it, in the sense that I don't want wiggles (big second derivaties across its trajectory.
So my plan is to:

1. Extract points from the spline.
2. Re-create a spline but only using a subset of the extracted points of the spline in question.
   I already extracted the points
   
   BUT now the Sketch-> Spline tool fails. It always creates a spline when I use two points. I therefore cannot create a spline with more than 2 points (which makes all of this pointless, well with two points actually ).
   What can I do to get around this?

I agree that it is unintuitive that the Spline tool stops when it snaps to a vertex. I will create a bug report.

There are tools that may help you:

• Wire Tools / Routings Tool Box / Approximate Wire
• Wire Tools / Fit Spline

The Approximate Wire tool allows you to specify the number of handles you want. It creates a parametric spline with handles (if Parametrize=True), so you can also edit it interactively by moving the handles.

I guess you can also create a spline using a list of points using the Python API.