Hi scott, how was the curve you're working on created, was it done only through drawing it with control points or were other operations done on it?

There are more things that can make up a NURBS curve than just the control points, stuff like a non uniform knot vector and weights. If your curve is structured using things like that, then just drawing a new control point curve through those same points won't produce the same exact shape.

Also another thing is your point selection start or end only on corner points? Because if not then that's another thing that will change shape as a new curve will touch the first and last point.

Could you please post an example curve so I could take a look?

- Michael