RE: what can cause this?
In answer to your level question, yes. The sight needs to be leveled to the bow. I level mine to the riser. The pins on your sight are most likely .029" . Copper John does offer .019" pins, though they are not as bright in low light. If you are watching the level, you may be lacking concentration on the target. I check my level as I come to full draw, then forget it, concentrating on the target.