Solution : https://service.sap.com/sap/support/notes/497649 (SAP Service marketplace login required)
Key words :
menu path 'media library' -> 'documentation' -> 'solution capabilities' -> 'component integration', menu option 'bdoc message' -> 'process' -> 'retry, calling system receives return codes 'e', menu 'bdoc message' -> 'process' -> 'retry, soap/xml outbound processing unlike idocs, crm middleware monitoring transaction smw01, menu 'edit' -> 'execute luw', solution idoc outbound processing, start stopped outbound queues, soap/xml inbound processing