PreserveOnRefresh on a Portlet

I have a vaadin 7.5.2 portlet that's exhibiting odd behavior when it's deployed in Liferay portal (6.2CE ga2, tomcat bundle).  The UI for the portlet does not have PreserveOnRefresh set. When I run it just as a stand alone servlet for UI testing I can see in the log and a Notification.show I stuck in the UI.init method that in fact the init method is being run every time I refresh, as expected. However, when it's deployed as a portlet the init method only gets called once regardless of whether I refresh the page.  The portlet is built using the self-contained approach so in either case the jars should be the same. Any thoughts as to where to look to solve this issue?

Update:  A little more investigation yields that it is behaving exactly as if @PreserveOnRefresh was set on the UI when deployed as a portlet. That is, UI.init is called once on the initial display of the portlet and subsequent page refreshes call UI.refresh . In the stand alone mode UI.refresh is not called and UI.init is called for each page refresh. I swapped out my custom component which was the content of the UI for a com.vaadin.ui.Label with no change in behavior. Is there some other place that PreserveOnRefresh can get set ?

Yes. It happens. Liferay might be adding preserve on refresh on top of Vaadin I guess.