Solution : https://service.sap.com/sap/support/notes/504127 (SAP Service marketplace login required)
Key words : 
attached source code corrections, purchase order item automatically, issue message v4295, variable message reason, update delivery address, purchase order, item level, -party item, delivery address, error message
Related Notes : 
       
| 204190 | Third-party: No update of purchase order with SP change |