Sorry for the double post, but here's a few explanations that could explain "The Enterprise Incident
deck two puzzle" in continuity, without considering it an error.
- The elevator system was unusually busy at that moment.
- Spock overrode the normal sequence, and took the elevator for a joyride, in order to talk to the commander for a minute.
- A cipher of some kind was automatically in effect, to prevent the Romulan commander from learning too much about the internal arrangement of the ship (cf "hours could seem like days").
- There was no cipher, but the elevator knew that in context "deck two" meant the second deck of sleeping quarters.