Biztalk FTP adapter caused ACK Zombies messages in Orchestration

We handled a strange behavior of logical FTP port in Orchestration which was set to Transmitted true.
In the Orchestration we had several send ports in a single none transcriptional scope. this scope also included call and start orchestration shapes.
The invocation of the orchestration left after each invocation two zombie messages , those was the ACK messages of the FTP adapter with the known error :

0xC0C01B4C The instance completed without consuming all of its messages. The
instance and its unconsumed messages have been suspended.

I tried to tweak the propertices of the scope to Synchronized true and also switch to different type of transaction. I know that such changes influence on the orchestration behavior , this I won't describe here.
Those changes didn't solve the issue.

Solution :
Finally I created another Atomic scope that included only the send ports , this configuration solved the issue.
That seemed to work fine but the error returned.
The problem was caused by using Send Port Groups, we have one group with two ports FILE and FTP. when we removed the FILE port from group we stopped getting the error.

In general you should always use Atomic scope if you have several send ports in a row , this save the Dehydration and Rehydration of the orchestration between each send.

Strange behavior of the adapter and orchestration mediation in Biztalk 2009.