Solution : https://service.sap.com/sap/support/notes/497367 (SAP Service marketplace login required)
Key words : 
delivery group correlation reason, /sapapo/bopbackorder processing, 'correlation' indicator, apodelivery group, delivery groups, backorder processing, 'worklist' tab, terms transactions, solution implement, implement note 505170
Related Notes : 
       
| 505170 | |
| 375193 | Backorder processing: Composite SAP note on posting |