Export as Step what is Bsplinesurface

 From:  BurrMan
11773.2 In reply to 11773.1 
In cam a “pocket” is USUALLY a 2d operation. Is you surface a simple 2d planar shape? Extract and use curves for pocket operation

If it is 3d, consider other toolpaths. A curved 3d surface cut would not normally be called a “pocket operation”

Maybe more info on your file can help?