Someone in the office recalls convos with Pioneer about this, and being told that it was a generic sat tuner in these models, not to Freesat spec and not designed specifically for UK use, so really anything you're getting should be viewed as bonus, rather than a given.
I have spoken to Freesat and my suppliers. I have retuned and rebooted the system. All other satelite channels are fine. I understand the bonus theory but I am struggling to understand the sudden loss of sound from only one station. So far no one has a logical explanation.