Solution : https://service.sap.com/sap/support/notes/184272 (SAP Service marketplace login required)
Key words : 
additional key words lock, function module 'dequeue_all', external processing operation, purchase requisition exists, form routine 'curr_order_delock', function module 'co_ru_order_dequeue', purchase requisition, form 'curr_order_delock', operation overview, order number
Related Notes : 
       
| 387386 | CO12/CORR: Locks deleted when pressing Enter/scrolling |