B2B adapter causes expired sessions in IS 46

We have about 5 B2BServerPackage adapters connecting to IS 4.6. Each time a document is sent to IS, 3 sessions are created that never get close and eventually expire. How can I get these sessions to close as soon as the called service is done executing? I’ve set the service to stateless but that has NO impact. I can modify that service to get it’s session id and then do a kill on the session, however, that only eliminates 1 of the 3.