I didn't read the other posts, so if I write something someone else already said, please excuse me.

I watched your bow-hand through all the shots. I think you should get a bow-sling and practice with your hand open. Just push the bow away from you, and let the sling catch it. It looks like you're 'twisting' the bow a little with the grip you have on it. And that's the purpose of a sling, to keep you from torquing the bow.

Other than that, maybe next time you shoot, when on arrow flies off from the rest of the group, mark it, and shoot again. Maybe you have one that's not flying like the others. It's possible.

Just my 2-cents. Hope you get it figured out.