Redirected to shopping_cart instead of checkout_success after order

[CTre]

I use an edited version of the COD payment module. Just the language is actually edited. It's weird I never previously had a problem with this, but recently after every order the customer is now directed to the shopping_cart.php page where it shows "Your Shopping Cart is empty!". Now the order shows in the admin as if it was processed, but its important to me that the customer sees the text in checkout_success. It basically notifies them that they need to check their email in order to complete the order.