Solution : https://service.sap.com/sap/support/notes/78757 (SAP Service marketplace login required)
Key words : 
set update task local, additional key words, similar situations, database commit, sequence problem, dequeue runs, time window, similar tasks, solution b30k027093, inconsistencies
Related Notes : 
       
| 118924 | Parallel processing of IDocs in the POS inbound | 
| 105604 | |
| 78935 | Duplicated update of IDocs in ALE Inbox |