Why doesn't VoiceOver want to focus on any app element?

Hi! I'm just asking for ideas why VO rarely but still decides to stop working with my app? I mean it focuses on status bar and no gesture is able to switch it back into the app. I noticed it always works perfectly with the login/registration views but fails with the views Inside navigationController. First it works partly - it recognises my top bar with a title, a search bar and so on but sees neither a table view nor a tab controller below. Maybe? it's connected to the fact every view inside navigationController has in viewWillAppear this code:

if UIAccessibility.isVoiceOverRunning {
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.8, execute: {
                UIAccessibility.post(notification: .layoutChanged, argument: self.navigationController)
            })
        }

Suggest please what could be the reason.