I'm using the dialog in navcontrol. If the app will be opened again from background to foreground, I always start in tabcontrol. When the app is in navcontrol and the dialog is opened and then pressing the homebutton, the app starts in tabcontrol. After switching from tabcontrol to navcontrol, the page is no longer reachable. It seems, that the system handles an open dialog, but the dialog is not visible.
When I close the dialog in application_background and start again the app in tabcontrol, the app jumps shortly to navcontrol and then back to tabcontrol. That works, but didn't looks professional.