I am tweaking now removing the bumps for the sand terrain. I am rendering a simple plant on a sand dune at 640x480.  The sand dune is smooth except in the distance where again I get artifacting or swimming or whatever along the edges.  It's a short 3 second piece.  Also, on the shadow of the plant that is casted on the sand - it swims like crazy even though the sand is smooth with slight rolling hills, etc.  No pebbles or rocks or sharp points.  I will link some samples later. tks for your response. 
I am hoping to have others chime in on this too....

Windows 10 - Poser Pro 2012 - 64Bit - 24GB RAM - 4 x 3.40 GHZ processor