I have always spin tested my broadheads. If you are shooting an arrow with an aluminum insert than more times than not there will me more glue on one side than the other. I simply heat up the broadhead, which in return heats up the glue around the insert. Turn it 3 times (by doing that you are evenening out the glue around the insert so it does not seat improperly) and if the spin test still shows a circular pattern at the tip of the broadhead then you need to take your time and center the insert. But all the things mentioned above will will be first on your list.I have always had excellent results in broadhead flight once i spin test them. Irecently switched to the Easton FMJ and with their insert design i no longer have to do this. 1 out of 12 arrows showed a slight wobble.