Hi Bravlin, that looks like a bug, I will investigate.

You can add a point by knot insertion instead of control point insertion though. That's when you click directly on the curve instead of on the control polygon. It's easiest to do that if you have control points turned off when you are in Add pt and then click on the curve. That will refine the curve in that general area without changing the shape of the curve.

It's normal when adding a control point to the control polygon that the shape of the curve will change a bit but the new control point is not supposed to shoot off like that.

- Michael