Who cut off your arrows and put the inserts in? If only one out of seven spun even then I would think that it could be the inserts are not square.

Also you have to remember any little twitch or imperfection in your form will be shown a lot more with broadheads then field tips. You could be shooting a little differently and not noticing the difference with the field tips but your are with the broadheads. I have a 3" circle if every one of my broadheads can hit in there then I'm satisfied that its in tune and the only way I can improve is by changing me not my bow. Since the target on a deer is probably a 8+ inch circle theres room for a little error as well.