Continuity mistake: When the crew are wheeling the Cat in the corridors of Red Dwarf, Kryten is holding onto the Cat's hand. In the next shot he is pushing the stretcher. (00:23:00)
Continuity mistake: When Lister drops the magazine in front of Rimmer it lands closed. When Rimmer begins to read it, it is open on the floor. (00:13:25)
Continuity mistake: When Kryten decides to be a mechanoid again, Lister gets up and grabs his jacket and swings it around his shoulders. The camera cuts to Kryten for a second then back to Lister, who now has his jacket on fully. The amount of time the camera was away from Lister would make this impossible for him to put the jacket on that quickly. (00:22:15)
Continuity mistake: In the scene where Lister is talking to human Kryten, just before Lister sees the photos, keep an eye on Lister's hat. It is perched on top of his head with about an inch of hair showing, yet the next shot shows the hat covering all of the hair, then it goes back to an inch of hair showing again. There is no time for Lister to have adjusted his hat between cuts. It is clear the line had to be re-shot. (00:12:35)
White Hole - S4-E4
Continuity mistake: Just after Kryten says what point in time he would like to return to, he is looking down and working with the screwdriver. The camera angle changes and he is looking straight forwards with the screwdriver on its side. (00:05:35)
Continuity mistake: Kryten has three spare heads but in 'The Last Day' in series 3, he only packed away one head. (00:18:40)
Continuity mistake: After Lister and Ace do the 'awooga' dance, Lister locks change from being clumped together to being mostly behind his back. (00:21:40)
White Hole - S4-E4
Continuity mistake: When the Cat and Lister are trying to cook an egg with a bicycle powered hair drier, you can see the Cat holding a frying pan. When Lister gives up and gets off the bike, Cat picks up a spatula with his other hand and starts poking the egg with it. However, in the next shot, he is shown with both hands on his hips. It's an instant cut with the same conversation continuing, so he didn't have time to put them down. (00:15:25)
White Hole - S4-E4
Continuity mistake: When Rimmer asks Kryten if it is the time of year his head goes for retuning, the shadow on his face changes between shots. (00:09:15)
Suggested correction: Lister can only see M-Corp products and M-Corp employees. Cat is not an employee of JMC or M-Corp, so he disappears. Lister is the only member of the crew who is employed by M-Corp at this point.
Suggested correction: Cat was a descendant of the cat Lister brought aboard Red Dwarf. Would it be possible that the new owners might have stricter security controls, and Lister was sent to Stasis for a different reason?
Andy Benham ★
Inventing Deux ex machina explanations for a plot hole doesn't make it any less of a plot hole. M-Corp erases all of the Jupiter Mining Corporation's equipment, personnel and infrastructure from Lister's life. In no way is Cat a part of that. He has no connection at all to the Jupiter Mining Corporation, and until he meets him in Episode 1 no connection to Lister, either.
If M-Corp only erased JMC equipment from Lister's life, then Kryten, who belongs to DivaDroid and not the JMC, wouldn't have disappeared either. He disappears as he doesn't belong to M-Corp, not because he belongs to the JMC. Cat has no connection to M-Corp, as he wasn't a part of the JMC (as you pointed out), and is therefore erased for Lister.