Solution : https://service.sap.com/sap/support/notes/402505 (SAP Service marketplace login required)
Key words : 
transportation planning/vehicle scheduling, additional key words transaction, attached source code corrections, prerequisites solution implement, /sapapo/bop_updatebackorder processing, backorder processing, /sapapo/bop, /sapapo/bop_result, loading date, determined
Related Notes : 
       
| 419232 | Backorder processing: TP/VS confirmation is not updated | 
| 418443 | Backorder proc.: TP/VS delivery date before desired date | 
| 416762 | Backorder processing: TP/VS scheduling incomplete | 
| 408885 | Backorder processing: TP/VS scheduling ignored | 
| 400517 | Backorder processing: Deadlines are not transferred | 
| 399301 | Backorder processing: Loading date not taken into account | 
| 399144 | Backorder processing: Delivery dates not known | 
| 396408 | Backorder processing: Error for scheduling | 
| 375193 | Backorder processing: Composite SAP note on posting |