Solution : https://service.sap.com/sap/support/notes/530828 (SAP Service marketplace login required)
Key words : 
warning message v1099 reason, issue warning messages, attached advance correction, information message, subsequent documents, purchase order, quantity change, sales order, subsequent document, quantity correlation
Related Notes : 
       
| 481464 | Incorrect correlation/processing after V4 message II | 
| 359714 | Warning messages from the quantity check | 
| 359265 | Incorrect correlation/processing after V4 message |