I've had a client tell us that they're getting e-mails (admin order confirmation email) that are different orders from the same person at the same time. After some test orders I've seen that what happens is when PayPal is used, and the customer is being redirected or has been, they then press the back button in the browser, amend the order and send it again.
This sends 2 e-mails to the shop and causes confusion. Is there a way to stop this? (Other than a big bold message warning not to do it)