@PreserveOnRefresh prevents setting attributes?

I have been doing a lot of research on VaadinSession in an attempt to figure out what’s going on when running a Vaadin application in a WebLogic cluster with session replications. One of the tests I did was to annotate my UI class with @PreserveOnRefresh. After I did this, attributes put into both the VaadinSession and the WrappedSession went mysteriously missing. The code is still running and calling the setAttribute() methods, but the attributes are just not showing up any more. As soon as I remove @PreserveOnRefresh, then the attributes are stored again.

Any thoughts?