Exactly what I was gonna say, spine and spin test. Sounds like your broadheads are not sitting sqaurely on the shaft. Have you spun the arrow to check for b-head wobble, nock wobble? If it wobbles AT ALL, spin the insert in the arrow 1/4 turn at a time until there is no visible wobble. Also, what size and type fletching are you using. You may not have enough fletch to stabilize the b-head. Also, straight fletch or helical may make a difference. If you are having any fletching contact with your rest, you will have trouble. I feel like it IS a tuning problem of some sort.