I'm been running into an occasional NPE in production with JSF after migrating from Wildfly 11 to Wildfly 14.0.1 ( Mojarra 2.2.13.SP4 -> 2.3.5.SP2 ) and I believe I've tracked down a small demo project that duplicates the issue. I've set the project to JSF 2.2 so it will deploy on both WF 11 and WF 14.

The basic problem is that when two pages with the same view id are loaded in separate tabs. From there is one of the tabs is posted and the result navigates to a different view id all references to that view id are removed from the view map. If the post does not navigate to a different view id then all works normally.

My assumption is that when the post navigates away to a new view id any reference to any page with the same view id is removed from the view map. This did not occur in Wildfly 11.

Additional clue is that even though the viewmap reference is removed the view scoped beans referencing it are not destroyed.

Demo project at https://github.com/codylerum/demos/tree/ee7/jsf-npe