Solution : https://service.sap.com/sap/support/notes/444854 (SAP Service marketplace login required)
Key words :
additional key words /sapapo/bop, /sapapo/atp_sd_order_get function module, account bythe backorder processing, enter /sapapo/atp_bop, enter /sapapo/bop_status_item, item_not_found raise exception, call transaction se91, _1/_2 item, choose 'long text', _v1_/_v2_ item
Related Notes :
| 511325 | Status of the item 'updated' instead of 'untested' |
| 481651 | Backorder processing: Termination due to missing category |
| 375193 | Backorder processing: Composite SAP note on posting |