Did you try to trace OpenConnection, SubscribeTable and CloseConnection callsas Dario suggests?
API issues unsubscription on it's own and connection gets lost.
Please can you clarify? Do you see unsubscription requests being sent to the server (can you attach a server log?) and after that the client closes the connection?

Please do not get confused by the unsubscription calls on the DataAdapter as those are not an evidence of the client sending an unsubscription request.