I can understand them taking your key card if you are changing rooms but not if you return to the same room.
Your key card is probably programmed for so many days and the last day of your cruise it will probably open
your stateroom door until about midnight.
I do not think it is an IT issue, it would just be the way key cards have to be programmed.
I think the only way to prevent something happening like someone going back to a room with an old key card
would be for Disney to have every key card manually deactivated as you leave the ship.
Wouldn't that be a nightmare?