I've raised this issue with SAP for them to assist in removing the negative value in Cash Discount Days 1 (ZBD1T) field.
Please see reply from SAP. Kindly advise if you approve that the SAP will update the documents with negative in Production. Please also check and confirm the list attached if that is the only documents with negative values, if not please provide the list of the documents with value.
Please see sample document in DEV520 - 1800000061 5151 2015, which was posted with negative value and then updated to have 0 value. The document will no longer encounter the runtime error.