Solution : https://service.sap.com/sap/support/notes/711876 (SAP Service marketplace login required)
Key words :
structure bapimepoitemx component component type grant_nbr bapiupdate func_area_long bapiupdate structure bapimepoaccountx component component type grant_nbr bapiupdate structure mepoaccountingx component component type grant_nbr bapiupdate, structure bapimepoitemx, fields grant_nbr, bapimepoaccountx, mepoaccountingx, prerequisites program error, terms purchase order, purchase order, functional area, account assignment
Related Notes :
| 1166562 | Problems during reassignment |
| 954531 | BAPI_PO_CHANGE: Field values are not transferred |