Rimmer goes back in time, alters the past, returns to the present, and he (and Holly) discover that he is alive, not a hologram. Then he accidentally kills himself and so is a hologram again in the next episode.
But, has the timeline been altered? So should Lister, Cat and Kryten from then on remember a past in which Lister and Rimmer both had been alive until "Timeslides"?
If so, shouldn't they remember someone else being a hologram?
If they have no memory of a live Rimmer (other than Series 1 Ep 1), why not? (Other than "Grant and Naylor don't worry too much about continuity").