Solution : https://service.sap.com/sap/support/notes/487090 (SAP Service marketplace login required)
Key words : 
/componentdata element/component typeposguid    cifposid, rule-based availability check, program error solution implement, apo backorder processing, request schedule lines, program corrections, sales order, partially delivered, bop reason, pibopxvbep structure
Related Notes : 
       
| 486793 | Backorder processing: Duplicate subitems | 
| 484343 | Backorder processing: initial MBDAT after update | 
| 375193 | Backorder processing: Composite SAP note on posting |