You could be torquing your release
I have had the same problem before, when it was a year before I picked up my bow. It took me a month to realize I was using my release wrong. Have an archery pro shop watch you at full draw, and make sure you are using proper back tension and not vertically or horizontally torquing your release. Since you are getting groups, the only other thing could be bowstring twist, or idler lean, or possibly cable guards over adjusted, from my experience. Hope this helps....