Loaded Commerce Community

My site runs CRE Loaded6 v6.2 Pro[13.2 (SP1)] and I've found that if you have available balance in your Gift Voucher account, go to make a purchase via PayPal module (to pay the outstanding amount that your gift voucher didn't cover), then before completing the payment go back to my site by using the return to merchant link on PayPal, not only has the amount of the purchase been deducted from the Gift Voucher account balance but the deduction has in fact been doubled! This can then lead to the voucher account being in debt.