Solution : https://service.sap.com/sap/support/notes/746102 (SAP Service marketplace login required)
Key words : 
supply change reason, source code correction, external procurement order, external procurement, purchase order, cdp characteristic, assignments disappear, purchase requisition, program error, problem occurs
Related Notes : 
       
| 444569 | Release restrictions for APO 3.10 Support Release 1 | 
| 427957 | Release restrictions for APO 3.0A Support Release 3 |