Solution : https://service.sap.com/sap/support/notes/405860 (SAP Service marketplace login required)
Key words : 
additional key words transaction, material availability date determined, material availability date, /sapapo/bop_updatebackorder processing, availability check, backorder processing, /sapapo/bop, /sapapo/bop_result, transportation scheduling, solution repair
Related Notes : 
       
| 387418 | Calling scheduling in APO-ATP controller | 
| 375193 | Backorder processing: Composite SAP note on posting |