The hearse that picks up the Ghostbusters at the train station already has the No-Ghost Sign on the doors in some scenes and a license plate that says "Ecto-1" before Winston turns it into Ecto-Jr. (an exact copy of Ecto-1, equipment wise) after the episode's half way point.
Ray's vampire gear vanishes and reappears at random.
Peter stated it was the first vacation the Ghostbusters took in three years, which seems to contradict Guess What's Coming to Dinner (1990) in which the Ghostbusters take two vacations.
After Winston converts the hearse into "Ecto Jr", the no-ghost logo on the doors appears and disappears from shot to shot.