PayPal Pro - Duplicate transaction

-- HikaShop version -- : 2.4.0
-- Joomla version -- : 2.5.28
-- PHP version -- : 5.4.37

This has only happened once, but its concerning that is happened at all.

We had a customer who had a duplicate transaction on Paypal when paying through the PayPal Pro interface. The Hikashop order only shows a single Paypal transaction ID, but Paypal had two distinct ones at more or less the same time and price.

Our previous cart application was able to avoid this even being a possibility by passing the invoice number along with the DoDirectPayment NVP call, which triggers a duplicate invoice check with Paypal.

We do have invoice numbers being assigned (same as the Order ID), but from looking at the Paypal Pro plugin, it appears there no way to actually associate that with the paypal transaction, since the payment is entirely handled during an onBeforeCreate action, which means the payment is complete in its entirety prior to an order number even being available.

While we can obviously refund this particular customer, we'd really like to figure out a way to prevent a duplicate from happening in the future. Any suggestions here?

Ah good point. The transaction in question was when we were still running 2.3.5.

Thanks! I'll keep an eye out for any duplicate transactions post-upgrade.

Hikashop 2.6
Joomla 3.4.4
PHP 5.3.29

I'm having the same problem using PayPal Pro plugin
Error 10536: The transaction was refused as a result of a duplicate invoice ID supplied. Attempt with a new invoice ID

How do I correct this?

We were first using the PayPal advanced plugin, but couldn't authorize without delaying capture. We switched to the PayPal pro plugin which allows us to add shipping when the order is picked, packed and ready to ship - shipping charge calculated and added at the time of shipment - on the PayPal interface.

In our tests, it appears the order / invoice ID gets stuck at its current increment when orders are not immediately completed. For example: the user begins the checkout process, but then decides to change the shipping or payment method. If the user doesn't clear the cart, logout, log back in, maybe clear the browser cache, close then open the browser to establish a new session - place a a test order using a non-PayPal method, then put a new order through checking out via PayPal Pro plugin, the order will succeed and confirm back through PayPal.

Your thoughts?