If I return to Duke's Store as admin after approving the shipment of a couple of items, and then click on List of Orders, the list is exactly the same as when I left it. The orders that shipped are still marked "Ready to ship". When I click View on an individual item, the status on that page is the same.
When I log in as the user who placed the orders, they are indeed shown as "Order shipped". And when I log out again and log in again as the admin, the orders are also shown as "Order shipped". It's only immediately after the status change that the incorrect status appears.
One wrinkle: If as the admin I deny a shipment, and then return to the list as admin, the status seems to have changed from "Ready to ship" to "Validating payment". This was the second item the user purchased, not the first, so this isn't the previous problem with the first order being perpetually in a "Validating payment" state (though that did happen the first time I tried using Chrome for Duke's Forest).