Using Mesh Features for Graphical Filter - sometimes chooses top and sometimes bottom

Create Terrain From Graphical Filter

Graphic Filter Manager

Filter Feature Type = Break lines

Civil Features selected include mesh that is to define terrain. The mesh is created from a template for a road that has points that run along the top of the surface and points that are directly below those points.

Sometimes the top of the mesh is used and sometimes the bottom is used.

In the attachment, the green shapes represent the pavement and the red lines represent triangles of the terrain that gets created.