NURBS surfaces are more likely to have problems when the derivatives along U and V are not orthogonal. This is only likely if we lathe or revolve around an axis that does not lie in the sketch plane. Also, all helical extrusions have this non-orthogonality in the U,V space and tend not to do well in intersection as shown here:

The errors go away if the axial displacement of the helix is reduced - as you get closer to a plain revolve.

The problem is that the function SSurface::ClosestPointNewton() assumes the derivatives are orthogonal. I have a fix in the works for this (works but I'm not sure it's quite correct). This may also be in play for #471