serialization callbacks called multiple times

the attached mvn project has session serialization enabled in the maven jetty plugin, and uses a serializable session factory in zk.xml
run with

mvn clean package
mvn jetty:run

open the URL

http://localhost:8080/test/generic-forward-composer.zul
http://localhost:8080/test/selector-composer.zul

wait a minute and observe the logs. when session passivation occurs, the "willPassivate" callback is called 3 times for the page using SelectorComposer and 7 times for the SelectorComposer.
Refreshing the page after session passivation, will call the didActivate listener equally often, each time with the same parameter. (Window)

Expected:

the listeners are only called once, or at least with unique parameters.

related forum topic http://forum.zkoss.org/question/97136/zk-653-session-serialization-didactivate-invoked-many-times