When a open customer or vendor transaction is marked for settlement, no modification on payment amount relevant data should be possible, except from where original transaction has been marked.

At the moment it is possible to modify cash discount relevant data on open customer transactions (in customer transaction form or details open or settlement form called from customer/customer transactions), even if the transaction is already marked for settlement in a not posted customer/vendor payment journal.

Which leads to differences between the amount in the payment journal line and the settled amount of the marked transactions, so payment or invoice line/vouchers remains open even if customer payment journal is posted.