An update.

I run the same small pocket test design with Cut2D this worked fine. With both MakerCam and Cut2D working okay the finger firmly points at VCarve. Both Cut2D and VCarve are Vectric pieces of software. My thoughts turned to application conflicts so I uninstalled both Cut2D and VCarve. I then reinstalled VCarve and run the test again, this time it worked perfectly.
It looks like Vectric cannot work with 2 applications installed. Thanks Phill05 for your suggestions.