Unable to Update Grips after trying to reconstruct a CustomCurveObject

Rhino Developer
1 
        public static void Initialize()
        {
            Rhino.RhinoDoc.ReplaceRhinoObject += RhinoDoc_ReplaceRhinoObject;
            Rhino.RhinoDoc.AddRhinoObject += RhinoDoc_AddRhinoObject;

        }
        public static void RhinoDoc_ReplaceRhinoObject(object sender, RhinoReplaceObjectEventArgs e)
        {
            if (e.OldRhinoObject is GradingCurve curve_o)
            {
                 if (e.NewRhinoObject is CurveObject polycrv)
                {
                    gripsToDelete = curve_o.GetGrips();
                    curve_o.GripsOn = false;
                    var res = Display.Doc.Objects.DeleteGrips(gripsToDelete); // Unable to delete these grips
                    
                    var gradingCurve = new GradingCurve(polycrv.CurveGeometry);
                    Display.Doc.Objects.AddRhinoObject(gradingCurve,null);
                }
            }
        }

how can I set the same grip to the newly created CustomCurveObject, so I can keep on editing the CustomCurveObject with ControlPoints without breaking?