As mentioned by @BirdTravels, for hand luggage screening many cruise terminals use the same/similar equipment as airports. The Smiths Detection 6040 is probably the most common but there are other models as well - they all usually have a limit of 24"x 16" for the tunnel opening.
For checked luggage that is somewhat different, but the above probably applies to many/most cruise terminals.
Yes, errors happen all the time, but if you really owed something on the cruise fare itself, your cruise would have been canceled by now. For peace of mind, you might want to invest some time in a call.
All JS on that deck have something above - you might switch to another to get closer to the elevators but taking a chance on noise issue with any of them (which should be minimal).
It probably comes up weekly so as long one browses these threads for about a week, you'd probably run across the cashing out via the casino slot machine in some thread.