That doesn't contradict the references in X, because they only say that Dave-Rimmer saved the ship. It doesn't mean Dave-Rimmer is a hologram of nano-Rimmer. Quite possibly I-VII-Rimmer-as-Ace came back and saved the ship, then for some reason quit wearing the wig and jacket. IIRC Dave-Rimmer has never expressed any recollection of events throughout Series VIII, only the very end. So maybe he swooped in from another dimension after the credits rolled.