Handing exception (in exception handler) from render response phase with forward/redirect is inconsistent

View.xhtml snippet:
<h:commandButton value="Submit">
<f:setPropertyActionListener value="#

{true}

" target="#

{bean.rendered}" />
<f:ajax render="outputText" />
</h:commandButton>
<h:outputText rendered="#{bean.rendered}

" id="outputText" value="#

{bean.value}

" />

Bean.java snippet:
public Object getValue() {
throw new NullPointerException();
}

Custom exception handler code:
if (PhaseId.RENDER_RESPONSE.equals(currentPhaseId)) {
try

{ nav.handleNavigation(facesContext, null, "/ErrorPage.xhtml?faces-redirect=true"); }

finally

{ i.remove(); }

}
Modify view and exception handler to achieve following combinations (HTML request = comment out f:ajax, forward = remove ?faces-redirect=true)

1) HTML request + forward: nothing in log, and malformed output is produced (no closing tags for </body> etc.)

2) HTML request + redirect: OK , redirect to ErrorPage.xhtml is done

3) AJAX request + forward: exception in log, bud no forward to ErrorPage performed

4) AJAX request + redirect: exception in log, malformed XML produced (<?xml and <partial-response 2x in output) , no redirect performed