Solution : https://service.sap.com/sap/support/notes/1067486 (SAP Service marketplace login required)
Key words :
update open credit values, vbuk-cmgst = 'b', terms olfmng reason, relevant support package, open credit, credit block, sales order, confirmed quantities, system behavior, partial quantity
Related Notes :
| 914627 | No open credit value despite confirmed quantity |
| 674112 | Updating of credit values in spite of credit block |
| 393304 | Confirmed quantity not cancelled in spite of block |