Solution : https://service.sap.com/sap/support/notes/387733 (SAP Service marketplace login required)
Key words : 
directly manufactured component, direct production reason, production order, assembly order, system generates, message co684, -order stock', program terminates, 'distribution rule, created automatically'
Related Notes : 
       
| 440912 | Settlement rule after extending subnetwork | 
| 377640 | Termination CO684 when creating assembly order | 
| 199651 | Termination when collective orders are expanded |