Big John - all three blades open - or did you try opening just one ?
Don't get me wrong, I'm not challenging you, but it seems like having just one open would upset the flight.
I agree with this.
If he is shooting a 100 grain broadhead currently and was shooting a 100 grain field tip before it isn't a spine issue IMO. A 100 grains is a 100 grains when you compair mechanicals to field tips. I would suspect blades opening on route to target disrupting the arrows flight.