ok , sorry but with this points i haven't intersections
that's a real situation.
lpt.Add(new Point3d(2526.11913296339, 4761.82097707599, 0));
lpt.Add(new Point3d(2250.71913296339, 4761.82097707599, 0));
lpt.Add(new Point3d(2299.01913296339, 4713.52097707599, 0));
lpt.Add(new Point3d(2526.11913296339, 4713.52097707599, 0));
lpt.Add(new Point3d(2526.11913296339, 4761.82097707599, 0));
the shape (black color) is regular, without intersections (i moved out from others lines in order to show it)
under this points we have some entities but the selection fails!