UISegmented Control hides below the UINavigationController - ios

Question

I have a firstViewController which has a UISegmentedControl and SegmentedControl has two tabs button. its all working fine but when i go to next SecondViewController. On SecondViewController there is a link for webView when i push to that webView & then back to SecondViewController and then back to firstViewController by tapping back button. The SegmentedControl leave its position & it moves below the NavigationController
firstViewController Code is :
override func viewDidLoad() {
super.viewDidLoad()
setupMenuBar()
setupViewControllerUI()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
setupNavigationBarUI()
}
override func viewWillDisappear(_ animated: Bool) {
super.viewDidAppear(animated)
// to avoid getting a black navigationBar while transition
navigationController?.navigationBar.barTintColor = UIColor.white
self.navigationController?.navigationBar.setBackgroundImage(UIColor.white.convertImage(), for: UIBarMetrics.default)
navigationController!.navigationBar.titleTextAttributes = [ NSFontAttributeName: UIFont.appThemeRegularFontWithSize(20.0), NSForegroundColorAttributeName: UIColor.lightGray]
}
// MARK: - UIViewController Helper Method
func setupViewControllerUI() {
if isFirstVC {
AppUtility.switchToViewController(viewController: firstViewController!, in: self)
segmentedControl.selectedSegmentIndex = 0
} else {
LoadingViewController.sharedLoader.showLoading(self.navigationController!)
AppUtility.switchToViewController(viewController: secondViewController, in: self)
segmentedControl.selectedSegmentIndex = 1
}
}
func setupMenuBar() {
SegmentedControlContainerView.backgroundColor = UIColor.ButtonColorWithAlpha(1.0)
segmentedControl.tintColor = UIColor.white
}
func setupNavigationBarUI() {
navigationController?.navigationBar.titleTextAttributes = [NSForegroundColorAttributeName : UIColor.white]
navigationController?.navigationBar.barTintColor = UIColor.ButtonColorWithAlpha(1.0)
navigationController?.navigationBar.setBackgroundImage(UIColor.ButtonColorWithAlpha(1.0).convertImage(), for: UIBarMetrics.default)
navigationController?.navigationBar.shadowImage = UIColor.white.withAlphaComponent(0.0).convertImage()
navigationController?.view.backgroundColor = UIColor.ButtonColorWithAlpha(1.0)
segmentedControl.setTitle("first", forSegmentAt: 1)
segmentedControl.setTitle("second", forSegmentAt: 0)
self.navigationController?.navigationBar.tintColor = UIColor.white
navigationController?.navigationBar.barStyle = UIBarStyle.default
self.title = "Screen Name"
navigationController?.navigationBar.setNeedsDisplay()
}