Revealing mistake: In the part in the motel where THING is doing morse code on the table to Gomez you can see the cut-out in the table where the guy's hand is sticking through the table.
Revealing mistake: The first time we see Thing running down the hallway at the start of the film, the bluescreen is visible at the top of the screen; where the wrist area begins.
Revealing mistake: During the Mamoshka dance, right when Gomez throws the knife high in the air (the one that lands in Fester's mouth), the camera goes to a wide shot when the knife is in the air, and you can plainly see that the jugglers are Fester and Gomez's stunts.
Answer: No doubt the Addams house had one of many secret, confusing passageways to get to the higher floors (and other parts of the house) from the vault that the viewer obviously is not privy to.
Scott215
It made me confused that if there's another secret way up to the house other than the slides or the bookshelf even though Fester had trouble finding which chains to pull but couldn't find the right one, If there was another way into or out of the vault and that means Fester had to know there was if Gomez was with him than Fester would have try the other one too instead of the bookshelf.
Trainman