Those notches are not from using shop air. If the cut gap is staying constant with the THC the nodes are probably from a setting in MACH. Make sure you have the CV enabled and CV Feedrate turned OFF. Watch the torch. If you are seeing ragged movement and hesitation in the cuts then it's a software/setup issue. If tuned right and it should move smoothly through the cuts.
Nothing like starting out on material that is a challenge to cut. Learning your machine by cutting mild steel is a lot cheaper and less frustrating way to optimize the cuts.
Cutting at .25mm? The charts call for .063 inches for cut gap which is closer to 1.5mm.
That's some pretty ugly cuts for a 40A tip.