Solution : https://service.sap.com/sap/support/notes/1058915 (SAP Service marketplace login required)
Key words : 
xi configuration parameter lock_message, error message 'object requested, terms qrfc reason, integration server remains, xi outbound queue, queue entry remains, parameter  lock_message, exception object, outbound queue, error text
Related Notes : 
       
| 1147287 | XI runtime: Preventing duplicate persistence | 
| 1118297 | XI runtime: QRFC processing of messages | 
| 987143 | Outbound queues hang in 'SYSFAIL' status |