GeomLProp_SLProps sometimes doesn't calculate normals...

Hi guys! Why GeomLProp_SLProps sometimes return false from IsNormalDefined() ? It's depended on IMeshTools_Parameters? or on resolution or on derivations?

Ordinary, this happens on sharp conical 3D models.

Handle(Geom_Surface) surface = BRep_Tool::Surface(m_occtShape);
static const double resolution = 0.001;
static const int derivations = 1;
{
                gp_Pnt2d uv = triangulation->UVNode(n1);
                GeomLProp_SLProps props(surface, uv.X(), uv.Y(), derivations, resolution);
                bool hasNormal = props.IsNormalDefined();
                if (hasNormal)
                {
                    gp_Dir normal = props.Normal();
                    if (face_reversed)
                        normal = normal.Reversed();
                    m_normal[nn1] = SMDVec3D(normal.X(), normal.Y(), normal.Z());
                }
                else
                {
                    //sometimes fall there...
                }
}