It is called broadhead tuning. First, make sure the 3 blade heads align with the fletching, and that they are balanced, (you can check this by spinning them and watching for wobble. You have several different choices. What is most likely going on, if the broadhead is properly aligned is that the blades of the broadhead are fighting for control with the fletching. You can switch broadheads, put smaller vanes on the arrows, or put a helicoil twist fleching on the arrows to increase spin. or you can broadhead tune the bow, using broadheads and field points. Or you can simply match your point of aim to the broadheads. there are different approaches, depending on his arrow/draw length and personal preferences. A good 4 blade broadhead, like slick tricks, will often perform just like field points when some 3 blades will not. A pro shop can fix you right up. these are the best suggestions I have without knowing his exact setup. This is why I encourage everyone to shoot those broaheads before season, better to find out now.