Solution : https://service.sap.com/sap/support/notes/419491 (SAP Service marketplace login required)
Key words : 
additional key words transactions, solution source code correction, update entries hang, error message sr053, backorder processing results, /sapapo/bop_updatebackorder processing, backorder processing, /sapapo/bop_result, executed method, allowed' appears
Related Notes : 
       
| 397814 | Backorder processing: no result update | 
| 397016 | Transfer of logical system in the CIF lookup table | 
| 375193 | Backorder processing: Composite SAP note on posting |