I JUST went and checked all the heads I bought at kzoo, all are ground nicely, and mount straight. Some older ones used to have ferrules that weren't perfect.
My heads from Bill @ Zipper have been nicely done. I just bought some more at kzoo. Finished well so just a little diamond stone work and they are scary sharp, ferrules are straight.
It's easy to see the wound channel is not straight, and when you hit ribs they actually shatter, not just split. The head spins through an animal. Not really fast, but it does. The more solid the medium is, the more it spins. So if you just look at lung tissue, tough to see any because the force of the lung tissue on the head is minimal. Through heart, muscle, ribs, and hide it is noticeable.
I'd try the zipper product again. I've had no problems.