Oscar and Nancy are pulling Felix up the dumb waiter to try to find people in their apartments to help them get out of the locked basement. Going by the establishing shot outside the building, they first attempt to find people on at least the fifth floor, which would make no sense, skipping the previous floors.
Oscar wears the chest/back plate of the armor backwards for the entire show.
There's apparently only one dumb waiter so how could it access all apartments on any given floor? Case in point is Felix and Philip's encounter. Philip lives next door to Felix and Oscar while Felix mentioned that the dumb waiter is boarded up behind the ice box.