Duplicate Orders (Paypal IPN and GV/DC)

A client of mine if experiencing a few duplicate orders using Zen Cart 1.3.9d.

The payment method is Paypal Website Payments Standard - IPN.

The biggest issue is the site sends software codes in the order confirmation emails which are quite valuable. Previously the same code has been sent in both but the duplicates have been deleted so I can't see them. Most recently though 2 different codes were sent which is a major problem.

In the recent occurrence the site has registered 2 orders, the first order on the overview shows the payment method as GV/DC followed by another order 10 seconds later by Paypal.

The same orders have been placed using the same discount code without issues so this is an intermittent problem.

I've read the other posts about possible browser related causes but the fix for this seems to be implemented in 1.3.9d. Also this is confusing as it's not a duplicate as such as it sees the Discount Coupon as a separate payment?

The GV/DC order does show the full value with the coupon deduction the same way the 'real' order does.

Upgrading to the latest version should help deal with some duplicate problems that would intermittently happen when using Website Payments Standard.

HOWEVER, the MOST EFFECTIVE FIX would be to click "Remove" on your Website Payments Standard module and click "Install" on your PayPal Express Checkout module, and of course configure it. Then you won't have any risk of duplicates the way the Standard module does.
You should still upgrade to the latest version for the benefits it offers.

Thanks, i'll give that a try.

I have looked at the updates but the store is customised in quite a few places so i'm reluctant to update unless absolutely essential.

Updating between 1.3.9 "letter" releases is simple ... just replace the changed files unless you've customized them. If you've customized them, simple re-customize the new file the same way.