All shaded-relief images below are lit at an elevation of 40 degrees, and are displayed with linear stretching.
Observe the annoying notches in a shaded-relief image of the 30-meter DEM at 120 degrees west. This is where the zone-10 DEMs merge with the reprojected zone-11 DEMs.
The Granger Northeast quad (left) has 20-foot contours, while the Sulphur Spring quad (sliver to the right) has 40-foot contours. This, combine with the way the contours bend near the quad boundary, is part of the problem. Such problems can occur at any quad boundary, not just at a UTM zone boundary.
This is the 10-meter DEM.
As I am not sure of the history of my 30-meter DEM, I recreated a patch with a nearest-neighbor resampling of the 10-meter DEM. Elevations are rounded to meters. I got lucky here; the faults fell through the cracks.
Here is the same thing, but leaving Z in decimeters.
This 30-meter DEM was created through aggregation, averaging the values of the 9 component cells. Z is in decimeters.