Solution : https://service.sap.com/sap/support/notes/588893 (SAP Service marketplace login required)
Key words : 
header-assigned network, terms sr reason, correct system behavior, existing settlement rule, distribution rule fails, settlement rule, distribution rule, system deletes, distribution document, bapi bapi_network_maintain
Related Notes : 
       
| 607000 | Required notes for PS-BAPIs |