Payment Discount being applied to Freight Lines - Cash Receipts

During the Cash Receipts process a given Customer is receiving a 2% discount on payment terms, this discount is supposed to apply to all item lines.  The problem is that if there is a Freight Line on the order, the 2% discount payment terms are applying to that line as well.  The invoice shows the proper discount amount (based on item lines) but in Standard Cash Receipt and the Customer Ledger the available discount is greater because the calculation is including the Freight Line.  Since the payment from the customer does not match the Open Amount minus the Discount, the