Solution : https://service.sap.com/sap/support/notes/531874 (SAP Service marketplace login required)
Key words : 
find sales document items belonging, 'goto' -> 'text elements' -> 'selection texts', error message /sapapo/atp_bop 031, backorder processing worklist, 'dictionary reference' indicator, filter solution implement, source code corrections, terms source location, items belonging, plant selection
Related Notes : 
       
| 533642 | BOP_NETCHANGE filter selects all planning objects | 
| 375193 | Backorder processing: Composite SAP note on posting |