If a commandButton returns navigation, the fileEntry listener will not run. In our testing, if the commandButton that submits the form containing a fileEntry returns a navigation case or navigation string, the fileEntry listener doesn't run at all. Since the listener also can't return a navigation case, the only way we have of routing the user to a different view after uploading a file is by doing a hard redirect inside of the listener. For optional files, we also have to dual-develop the navigation - once in a button that doesn't have the file and returns a navigation, the second time inside the listener.

Please see attached fileUploadProblem2.xhtml for a demonstration. The first submit button is not wired to an action. The second is wired to an action that returns null. Both work. The third is wired to an action that returns navigation. It fails. You can see in console that the UploadBean's "Set a file" output is never produced.