Geometry issues - surface thickening

Hi All,

Having some serious trouble getting this part to behave. I can't find anything wrong with the surface - all I know is that something about the radii in the master model is causing the extrusion to fail.

The thicken is working okay, but I want there to be a flat surface on the bottom of the housing, and the extrusion continues to fail (see screenshot). What's weird is that the mirror of this piece, the left housing, works perfectly fine. SW is just hung up on this side and I can't figure out why.

Any advice???

EDIT: The flat (cut) needs to go through the origin of the part.

SolidworksSurfacing