Also like Brian mentions in order to be able to cut the knurl the surface must fully divide it into different sections.

It looks like you may have some areas where the cutting surface is only partially submerged in the knurls and not fully dividing it, like in this area I've circled in red here:




If possible it can be easier to use a 2D profile curve as the cutting object rather than a 3D swooping surface.

- Michael