Solution : https://service.sap.com/sap/support/notes/578278 (SAP Service marketplace login required)
Key words : 
terms apo-atb-bopbackorder processingboprejected status/sapapo/bop/sapapo/bop_resultcave_sl_doc_inbound_bop reason, update complete status, apo backorder processing, problem occurs, program error, solution implement, program corrections, implement note 578625, related program, processing
Related Notes : 
       
| 628948 | Performance of BOP update in APO | 
| 578625 | BOP: 'Rejected' status inadvertently set | 
| 375193 | Backorder processing: Composite SAP note on posting |