Hi
I already tried to get all of the items and you can get all of the quest items after a cooldown (I don't know yet if it's 20 or 24 hours for some).
I got a second wind-up loco today from the same chest.
However, if you finish the quest and kill Lord Retro you cannot get items anymoreanymore, but the Tibia Coin I have been getting more, everything else I get the message "The Chest is empty".