Shopping Cart is Processing a Payment Twice

-- url of the page with the problem -- : www.genealogysa.org.au
-- HikaShop version -- : 2.3.2 business
-- Joomla version -- : 2.5.24
-- PHP version -- : 5.4.27
-- Browser(s) name and version -- : Chrome 40.0.2214.111 m
-- Error-message(debug-mod must be tuned on) -- : No error message

We have around 300 successful purchases per month. One or two of those generate two payments about three seconds apart. Our payment processor eWay process the credit card twice, and Hikashop records two orders and two payments and sends out two sets of Emails to the user and to us. Our Shopping Cart is set up fairly simply, (Cart/Login/Cart/Payment). I thought Hikashop would catch this attempted double payment, but I have no idea what what is happening. Thanks for any help.

Hello,
Firstly, can you download the last Hikashop version through our website, install it and test it again ?

Thanks, but I cannot upgrade till I find out what custom code has been inserted, and have a way of repairing the code after the upgrade. I can't believe that this has not happened to anyone else, but if no-one has any ideas, I will have to find a way to upgrade . . .

Thanks Nicolas, I will organise the upgrade and report back if the problem recurs.