After a second viewing I now realise what bothered me about the Emperor scene. When viewed side-on the Emperor looks like he is mostly a single still frame, animated by the static and jitter of the poor signal. It’s most apparent in the final shot where he appears frozen with his mouth open for a few seconds before closing it towards the end.
It’s still a great improvement over the blu-ray version where they re-shot Ian McDiarmid looking nothing like the ROTJ Emperor who apears only months later in ‘Retun’.