Duplicate messages received by BizTalk

I recently witnessed an issue with AIF in Dynamics AX 2009. The system uses BizTalk adapter to send messages to a subsystem. It was working fine till recently. All of a sudden, we found that BizTalk is receiving multiple messages for each message sent out of AIF.

Here are the symptoms:

• Send messages out of AX using AIF
• Message is successfully sent out and can be seen in document history
• After that, message stays in AIF Queue manager for 10-15 minutes
• In these 10-15 minutes, BizTalk receives the same message multiple times(5-12 times)

What we tried:

• Running AIF receive/send related 4 classes using a job
• Tweaking AIF global settings (disable caching etc)
• Restart AOSes (its a clustered environment)
• shut down one AOS and one BizTalk instance
• No luck after all the above

Here is the solution proposed by MS support:

• Create a new configuration and restart AOS and BizTalk
• Duplicate issue is resolved
• We reverted to the original configuration but Duplicate issue didn't arise

I suspect some where sessions/previous Business connection session information is stuck and the new configuration cleared it up.