Other mistake: When Lister inadvertently sets off the Auto Destruct sequence, the computer voice says the ship will detonate in 15 minutes. The computer then says "the ship will detonate" every five seconds followed by how much time until detonation, but the time in which the computer says this is inconsistent. Two seconds after the computer says 15 minutes, the computer says the ship will detonate in 14 minutes 55 seconds. Ten seconds after saying that, the computer says the ship will detonate in 14 minutes 50 seconds. (00:01:50)
Revealing mistake: After landing on Earth, Rimmer and Kryten are standing on land. When Kryten asks "What is this place?", a car can be seen driving forwards in the far background, even though everything in this version of Earth is supposed to work backwards. (00:06:15)
Other mistake: It is established in the backwards version of Earth, that all writing is reversed and is spelled backwards. However, there are some inconsistencies, as in some instances the writing has been mirrored to appear reversed, whilst in some instances the writing has just been spelled out backwards. For example, car number plates and signs on display in the background have been mirrored to appear reversed, but the newspaper that Kryten reads, the Nodnol sign and the Sensational Reverse Brothers poster appear normally typed out, and not as the mirror image that other aspects of this world have.
Continuity mistake: When Lister goes into stasis, Todd Hunter turns the wheel on the door to lock Lister in. In the next scene when Lister awakes from stasis, he just pushes the door open without turning the wheel to unlock it. Even if we are to assume that Holly would automatically open the door, the wheel should still turn to unlock the mechanism.
Continuity mistake: When Rimmer shows Lister the luck virus and sexual magnetism virus, there is less than half of the liquid shown in the test tube for the sexual magnetism, but when Rimmer is about to go to Hollister's dinner later on, there is more liquid in the test tube. There was also only one test tube of sexual magnetism for Rimmer to use. (00:12:15 - 00:18:10)