I need to apply an initial prepayment of 30%, a 2nd prepayment of 40% and final prepayment before shipment of 30% but I only have one product, quantity of one and if I apply the first 30% and create an invoice for the second and third payment it cannot be applied because the purchase order has already been grabbed by the first prepayment. 

any ideas or workaround to bypass this issue?  is there a fixed in a later patch?  we have v12.p26

any help will be appreciated!