I think it was something like "If Lister hadn't been imprisoned in stasis for smuggling a cat on board, he would have been there to help me mend the drive plate, so I wouldn't have made the mistake which caused the failure, which killed all the crew".
Lister smuggled the cat that caused the malfunction on to the ship in the first place unless I'm remembering that wrong, but I haven't seen Red Dwarf in about 2 decades.
Rimmer was 100% assigned the responsibility of repairing the drive plate that released the neutron blast that killed the entire crew of Red dwarf.
However, in all fairness, everybody on the ship knew that rimmer was incredibly incompetent and assigning him such an important responsibility was a failure of command, so the real person who killed the entire crew was whoever ordered rimmer to do the repair.
Lister was already in stasis at this point so he literally could not be responsible for this.
Fair enough, it's been 20 years. I just thought the need for the repair was caused by the cat, which would have been Lister's fault for sneaking the cat on board in the first place.