Exporting spline sketch to DXF correctly

I'm trying to model a line drawing of a coaster I want to CNC cut. I've sketched it out fine (Using mainly splines), but when I try to export it to DXF for my CAM software, most of the splines become straight lines! I've tried auto dimensioning the freehand sketch with the same issues....

I've attached the part file if anyone can see what's wrong?

James

SolidworksSketching