I am finding a matching line on a Vendor Bill Payment and checking the apply box. There's no other manipulation going on but when I do this, I get an error of "NEGATIVE_BILL_PAYMENT_ERROR_MSG - Negative Bill Payment is not allowed" but you can create payment from the Vendor Bill and check the apply box on the resulting Vendor Payment just fine.. So works in UI doesn't work in Script but its doing the same thing. Anyone seen this one (SuiteAnswers is no help on this one for dev)?