Solution : https://service.sap.com/sap/support/notes/451511 (SAP Service marketplace login required)
Key words : 
additional key words /sapapo/bop, product allocation assignments, product allocation assignment, interactive backorder processing, original schedule line, solution implement notes 435343, backorder processing, /sapapo/bopi, schedule lines, implement note 456825
Related Notes : 
       
| 456825 | |
| 446299 | BOP: Problems in the postprocessing | 
| 445257 | ATP view/planning data consistency in interactive PP/DS | 
| 439745 | BOPI: New delivery schedules / scheduling | 
| 435343 | Backorder processing: Item does not exist | 
| 375193 | Backorder processing: Composite SAP note on posting |