Cross Section Surface Errors

I have been seeing some Errors in the Terrain model display in SS4 InRoads.  The image below shows what has been happening.  The red line is the DTM from and SS2 cross section while the green line is the exact location showing an SS4 display of the original ground.  The red line is correct and the green is not.  Any reason why terrain models would not de displayed correctly in the SS4 cross sections?  I have look at the actual terrain models triangles and they do match exactly in the models i.e. triangle leg for triangle leg between SS4 and SS2 surfaces.  The one main difference is the Triangles in SS4 are a mesh due to the nature of the SS4 triangle display.  This has become a pretty significant issue, it seems to happen quite often.  This happens in the dynamic cross section view and the plotted cross section.