This happens to Carbon ICS type arrows much more frequently than many suspect, and in fact within a new dozen one usually finds a few of the arrows don' t spine match. Either of these scenarios or a combination thereof result in flyers and arrows that just won' t group. It is a lessor problem with pultruded carbon shafts, and non-existent in ACC and aluminum unless the arrow is bent as there is really nothing to degrade...

This is the main reason I switched to ACCs and have never looked back. Consistency from arrow to arrow, shot to shot.