I updated to 1.18 and started seeing duplicate orders again… but what it turned out to be is that customers are attempting mulitple times to checkout as there is an error when they pay with paypal express…
You add to cart, go to checkout, click thorugh to paypal. Now on the paypal screen you login and then see the PAY NOW button. Up to now everything is fine (pending order in admin and all)… but when I hit the PAY NOW button it takes forever to process… meanwhile in the admin the order is set to processing (Paid) and paypal continues to twirl.
Eventually the customer sees something like this:
Transaction refused because of an invalid argument. See additional error messages for details.:
A successful transaction has already been completed for this token.
I hadn’t changed any of my paypal options or settings in the admin of paypal or magento… so does anyone have any idea what’s going on? Or how to debug it?