InRoads XM Contour Labels

Problem: 

Why do my contour labels disappear? 

When labeling contours I use the "Surface>View Surface>Contours" Command.

When I set the contour intervals to 0.5' everything looks OK.

But when I set my contour intervals to 0.1' the labels appear as expected on the south end of the DTM, gradually disappear as I approach the midsection of the DTM, then are completely absent on the north end.

Besides manually labeling the contours (by using the contour labeler) is there a way to fix this problem?

See the attached PDF for example of the problem free section (south) and problem area (north) using the 0.1' contour set. 

DTM: 

200 ft wide Runway with a profile grade of 0.2% (from south to north) and constant 1.5% cross slopes (crowned) for a length of 9,000 ft.  There is additional pavement and grading beyond the ends.

I designed the runway using the Roadway Modeler, making the runway one continuous corridor and intersecting Taxiways, service roads, and aprons each a separate corridor. 

I do not know if how I set up the model would affect the outcome when labeling contours.