Solution : https://service.sap.com/sap/support/notes/539151 (SAP Service marketplace login required)
Key words : 
-explanat'r' indicator, manual transfer postings, attached program corrections, created transfer requirements, message class c2, posted goods issues, wbs element reason, existing settlement rule, wbs element change -, message short text
Related Notes : 
       
| 538667 | No or incorrect goods issues for confirmations | 
| 524401 | Change of WBS element not updated on components | 
| 428052 | Settlement rule adjustment at WBS element change | 
| 413269 | CO02: Inheritance of WBS element from header to component |