Sure you are shooting instinctively ? "felt I was aiming at the moon" How you shoot doesn't matter, but, I guess you need to decide if you are aiming (using a sight point) or not.
At twenty yards, things can affect the arrow flight that much , yes. Little things such as where you are anchoring, how straight upright you are / were standing, are you coming to full draw, is you bow hand exactly the same as it was earlier, with three under, are you applying equal pressure to all fingers or most on the top finger, etc etc. Sometimes little things change the whole game.
ChuckC