EDIT: It seems that it is the way i did the 3D model. I use Autodesk Inventor and flipped the extrusion direction and it worked. Is this a known problem / necessity when creating things for CNC Milling? I always try to constrain my objects properly on CAD. I GUESS it makes sense geometry wise that you would have do this, but it seems like this type of thing would be automated / more streamlined, well i learned something today!