Solution : https://service.sap.com/sap/support/notes/399547 (SAP Service marketplace login required)
Key words : 
prerequisites program solution program correction, additional key words bop, remaining quantity item, requested quantity, location determination, product substitution, run reevaluation
Related Notes : 
       
| 394471 | Backorder processing: BOMs | 
| 375193 | Backorder processing: Composite SAP note on posting |