RE: broadhead groups...
I had kinda the same thing happen to me.
I got tired of busting arrows so I mentally made myself stop group shooting. When I had to have my string replaced and had to resight everything back in, I could not group shoot for crap. I could shoot a single arrow in side of a bull's eye at 40yds ona consistant basis, but when I tried to group shoot I couldn't do it. And the closer I got, the worse my groups got.
It took over a week to get my groups together. All I could see in my head when I released the arrow is the $100 that I paid for that dozen.