I don't understand why everyone is so infatuated with pass throughs, however, i'd say shot placement/angle are at fault, what kind of penetration were you getting, a lot of times if an arrow blows through bone on the way in and hits bone on the way out, it will stop dead. not knowing where he hit these deer , im going to guess and say he was aiming for heart instead of lungs. the lung shot is by far the best for a complete pass through