A couple of thoughts
1) Is the bow actually pointing at the centre of the target when it's shot? i.e. if you stand behind your partner when they're hitting the gold, does centring the string on the limbs just before release also align with the centre of the target? If the bow is pointing off to the left then that could explain why the sight is off to the right. I've just seen this with someone at our club who's shooting GMB scores in practice and was concerned about the sight being well to the right - At 70m the bow was aligning with the white at 9 o'clock despite good groups landing in the gold. Haven't quite figured out how that works yet - but it did explain the sight position.
2) Head position? Anchor? I'm not convinced that there is a single correct sight pin position because what happens if you start with a theoretical situation of everything being well tuned and aligned with the target, your sight pin being where you expect it to be and you're hitting the centre of the target. So when the eye, pin and spider align, the bow is pointing in exactly the direction it needs to (it's hitting the centre), but what then happens if you lean your head slightly to the right? - the bow is still pointing where it needs to, but the pin would now appear be off to the left of the line between your eye and the spider, and would need moving further right to bring it into the correct alignment for that head position, lean a bit more, and the pin would need moving more. But also what if there is no leaning, just a different facial shape, eye separation, head rotation, anchor point etc, all of which can potentially give a different lateral offset between the sighting eye and the nock, and so need a different pin position to compensate.
If the bow is well tuned and producing good results (which it sounds like it is) is it something to worry about?