In the Roughing and Profiling cycles, check Detect Flat Land (Depth tab) to make sure that there is a cutting pass at the height of any flat region.
Without this option checked, the last (lowest) pass occurs when there
is not sufficient depth remaining for another full cut (as specified by
the Cut Increment).
We recommend to leave the
option unchecked when working with large surface parts with no flat areas
to increase processing speed.