Solution : https://service.sap.com/sap/support/notes/497172 (SAP Service marketplace login required)
Key words : 
rule-based availability check disappear, apo backorder processing, main item consists, request schedule lines, created due, symptom occurs, sourcing reason, program error, solution implement, program corrections
Related Notes : 
       
| 498795 | Backorder processing: Several request schedule lines | 
| 495273 | Backorder processing: several request schedule lines | 
| 493656 | Sales order items not updated in the OLTP system | 
| 375193 | Backorder processing: Composite SAP note on posting |