AppFabric Message Buffer does not seems to behave like a queue

We are on a PoC regarding distributed application that leverages AppFabric Message Buffer. My colleague experienced that message buffer does not always behave like a queue. From what I understand message buffer messages are in FIFO manner.

What my colleague found out was that he stored 5 messages to the message buffer then moment later he stored his 6th message. A separate console application retrieving messages got 6th message first then the other five messages in order. 

We are still trying to recreate what happened.