Solution : https://service.sap.com/sap/support/notes/115995 (SAP Service marketplace login required)
Key words : 
additional key words unbw, generate settlement rules automatically, settlement rule manually, lower-level orders, settlement rules, collective order, upper order, material type, program error, solution carry
Related Notes : 
       
| 119159 | Collective order: Material type is non-valuated | 
| 63601 | Production order for non-valuated material |