Problem: in load balancing environment time-to-time sessions are dead in Active sessions pool. (ad_session.isProcessed=N). Actually Sessions are "deleted" when server started. (ad_session.isProcessed=Y - according to discussion with CarlosRuiz.)
Solution: We agree with CarlosRuiz would be solution to improve shutdown process by - similar to start session - to "clean ad_session"
IMPORTANT: server must process only related session, not other servers session.