Expired discount in cart but PayPal still accepted it?

[intandem]

Can anybody shed light on this situation please? My client had a discount voucher code set up that expired on Monday evening. Today, she received an order from a customer using this discount code. The PayPal receipt email my client received shows that the discount was applied. However, in the Prestashop backend it showed the order as having an error. 

 

My client told me that she noticed the customer's name on Monday attached to an abandoned cart. We are now wondering whether the customer created a cart while the discount was still applicable but did not complete payment until after the discount expired. So somehow the order amount incl. discount was submitted to PayPal but Prestashop recognised the error. But we of course don't know for sure if this is what happened. 

 

Is this a bug or should we have done something else in the settings??