Solution : https://service.sap.com/sap/support/notes/378378 (SAP Service marketplace login required)
Key words : 
additional key words transaction, rule-based atp, symptom remaining requirements, /sapapo/bop_resultbackorder processing, remaining requirements, backorder processing, /sapapo/bop, scheduling line, oltp system, problem occurs
Related Notes : 
       
| 378745 | Backorder processing: new sub-items are missing | 
| 375193 | Backorder processing: Composite SAP note on posting |