PJ,

A buddy of mine made a marginal shot a buck a few years ago and rather than run away the deer stood in a tough spot at about 40 yards with a small window to the vitals........with the second shot he misjudged the yardage a bit and shot right under the wounded animal.
With the 3rd shot (and the last time he will carry only 3 arrows he had the little rubber band on his Rocket expandable roll off as he pulled it from his quiver because he was excited.
He decided to try a shot with it anyway as it was his last chance and he wanted another arrow in the vitals. The blades stayed closed at full draw but when shot I think his exact words were that the arrow looked like a "Wiffle Ball" in flight[:-].
Not even close.

I think when things leave the bow in a certain position the flight characteristics are very much different than if something changes with regards to aerodynamics in mid flight.
I was having trouble with a certain brand vane staying on the shafts and had 2 instances where one flew off in mid flight and the arrow actually curved to target like a paper airplane.
The same arrow shot with only 2 vanes flewbasically astrue as the rest, but the midflight change was dramatic.
I don't imagine a single blade flopping down in mid flight of an 1 1/2" cutting diameter mech head would be conducive to good flight either.