I am having a problem with the Z axis skipping during 3D contouring. It doesn't lose count but doesn't keep up with the motion of the X and Y axis. I am using V3.5.1 software with NC code generated from MasterCAM. The machine is a newer PRS Standard. I have tried taking the feedrate down to 40IPM/.66IPS and still have problems. If I run a contouring routine where I am stepping down and running just the X and Y axis it makes a perfect cut at speeds up to 3IPS. The slides on the machine are clean and there doesn't seem to be any binding or roughness.

Any Ideas?