The identifier that is being logged, is the identifier of the message that failed. If you see messages that have a correlationId with that same identifier, that means that there was a message that was generated as a result of processing the message with that identifier.
In other words, the first entry represents the message for which processing failed. The second message is a message that was generated as a result of processing the first (either by the failing handler, or another one).
Hope this helps.