HI Crusoe - this is a display problem, your actual geometry is fine.

On certain "S" type shapes the display mesher can get confused and not add enough polygons. This doesn't happen on the export mesher because the export mesher does a much more careful job of analyzing the shape of the surface, but the tradeoff is the export mesher is much slower.

There is a setting you can turn on to fix this up - go to Options and check "Add detail to inflections":



That will increase the density of the display mesh in certain areas and give more detail to the display. I'm thinking of switching this to be on by default, the only reason it is not on is that it creates more polygons which can slow things down a bit on complex models.

- Michael