Solution : https://service.sap.com/sap/support/notes/184914 (SAP Service marketplace login required)
Key words : 
customer-specific copy routine, copy routine fv50c001, terms vbak-waerk, delivery document level, sales order consistent, prerequisites currency evaluations, customer currency, sales order, delivery document, statistical evaluations
Related Notes : 
       
| 1521933 | Sold-to party filled in outbound delivery for pricing | 
| 751071 | SIS: M2802 error when determining local currency | 
| 185042 | SIS: Update value fields in delivery w/o order reference |