Solution : https://service.sap.com/sap/support/notes/385472 (SAP Service marketplace login required)
Key words : 
filter parameter check tab, additional key words transaction, prerequisites solution implement, source code repairs, symptom items, /sapapo/bop, /sapapo/bop_result, /sapapo/bop_update, backorder processing, confirmation
Related Notes : 
       
| 434415 | Backorder processing: Filter for cancelling the confirmation | 
| 420605 | Composite SAP Note for BOP performance in APO 3.0A | 
| 409801 | Backorder processing: item (confirm. cancelled), no update | 
| 383514 | Backorder processing: Incomplete transfer | 
| 380703 | Backorder processing: Documents with unchecked status | 
| 375193 | Backorder processing: Composite SAP note on posting | 
| 372123 | Backorder processing: Update is incomplete | 
| 328339 | Backorder processing: Cancel confirmation |