SwiftUI: External screen view not updating after app comes back to foreground

Question

I need to use external screen do lyrics projection (I develop app for chords & lyrics). Everything works fine until I move app to background and back to foreground. View on external screen is not updating (on appear it shows correct number and then does not update).

You can see the problem here: https://media.justchords.online/SwiftUIExtScreenProblem.mov

Settings in Info.plist: EnableMultipleWindows = YES SceneConfiguration / External Display Session Role Non-Interactive: Configuration Name = External Delegate Class Name = $(PRODUCT_NAME).ExternalSceneDelegate

Test view for external screen:

struct ExternalScreenTestView: View {
    @ObservedObject var counter = TestCounter.shared
    
    var body: some View {
        Text(counter.count.description)
            .font(.system(size: 50))
    }
}

class TestCounter: ObservableObject {
    private var timer: Timer?
    @Published var count = 1
    
    static var shared:TestCounter = TestCounter()
    
    init() {
        self.timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { _ in
            self.count += 1
        }
    }
    
}

My SceneDelegate:

final class ExternalSceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?
    var controller: UIHostingController<ExternalScreenTestView>?
    
    func scene(_ scene: UIScene,
               willConnectTo session: UISceneSession,
               options connectionOptions: UIScene.ConnectionOptions) {
        
        guard let scene = scene as? UIWindowScene else {
            return
        }
        
        let content = ExternalScreenTestView()
        window = UIWindow(windowScene: scene)
        controller = UIHostingController(rootView: content)
        window?.rootViewController = controller
        window?.isHidden = false
    }
}