Man o man... There are so many things that can cause stuff like that that I can't begin to know what to do to help you. Is the bow tuned? Are your arrows correct for the bow? Did you get a good release or did you pluck the string? Are you concentrating as much on the 20 yard shot as you did on the 30 yard shot? Is your shooting form consistent from shot to shot? .... Did you take the shots during different moon phases?[8D]
Honestly, this is something that you really need some face to face help to cure. But I'll take my best stab at what I think MIGHT be a problem... Your release.
I don't like using the word 'release' for shooting fingers. I like the old English term 'loose' better. 'Release' is telling you to do something. 'Loose' is telling you to stop doing something. A very key point.
Your fingers cannot move fast enough to get out of the string's way to release it, soyou mustlet it loose. You are holding the string back. When you're ready to shoot, just stop holding it and let it escape. It'll simply push your fingers out of the way and go.
Now, you don't want your hand flying out sideways, away from your face after you loose. It must come straight back. So, part of the loose is accomplished by pushing your elbow straight back as you begin relaxing the fingers to let the string escape. That keeps you from plucking the string. A string pluck will put a really hairy sideways oscillation in the string, which will always make the arrow fly off course. And that's bad!
Like I said, there is no way for me to know if that's your problem, but it's always good to review basics of a fingers release anyway.
Shot Consistency
