Solution : https://service.sap.com/sap/support/notes/35047 (SAP Service marketplace login required)
Key words : 
additional key words delivery block, credit limit release, manual blocking reason, avoid syntax errors, credit limit check, availability check, confirmed quantity, sales order, install notes 19180, solution correction
Related Notes : 
       
| 33078 | Credit check: Blocked documents are approved | 
| 31248 | Release, another check and block, performance |