Solution : https://service.sap.com/sap/support/notes/448431 (SAP Service marketplace login required)
Key words : 
solution implement source code corrections, additional key words transactions, product allocation procedure, /sapapo/bop_resultbacklog processing, /sapapo/bop, backorder processing, incorrect allocation, order items, problem occurs, allocation
Related Notes : 
       
| 375193 | Backorder processing: Composite SAP note on posting |