You’re at the vending machine. You tap in the number for a bag or crisps.
The bag of crisps starts to move but get caught on something, so they don’t drop into the bottom. Instead, they’re left dangling.
The machine somehow knows this happened and so doesn’t charge you for the crisps.
You still want the crisps so put the money back in and press the button again. This time the packet of crisps behind the dangling crisps starts to move, drops and in doing so knocks the dangling crisps into the bottom too.
You have two bags of crisps but have only been charged for one.
Do you keep both bags of crisps? Or do you leave one bag in the bottom?