Skewed DEMs load with bad data
If you load a DEM with a slight, or not so slight, skew to it, MB will load the DEM into a straight square and fill in the empty tiles with -32767. ALL DEMs that are not perfectly in alignment with the X-Y plane will have this issue. This becomes a visualization issue when the DEM is loaded (since the automatic range is way off) and these false values are also picked up by the interpolator.
This happens on 4.2 and 5.0