Like what was previously stated, if you have arrows that do not shoot left compare them in flight. A bow that is not center shot can have a different reaction to arrow spine than a takedown recurve. The cant of the bow, the grip, the archer peeking to watch an arrow fly can change the head position. It could also be that his first arrows were flying to the right and he adapted to them, so now the new heavier arrows seem to be going left. If the arrows are very stiff, often they can be heard clipping the bow. Perhaps a bit more brace height can show an improvement.