Large title in Navigation Bar glitching when pushing another View Controller

Whenever I push to a new View Controller, a weird animation glitch where the title stays even after another view controller is loaded and does not animate to the back button. It only happens while pushing to a View Controller when large title is showing. I cannot understand why it's happening.

This is my Main View Controller.

'''

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var tblUserList: UITableView!
@IBOutlet weak var scrollView: UIScrollView!
@IBOutlet weak var constTableViewHeight: NSLayoutConstraint!

let searchController = UISearchController(searchResultsController: nil)

let names = ["Rajesh Hamal", "Rishi Dhamala", "Salman Khan", "Shilpa Shetty", "Majnu Bhai", "Uday Shetty","Rajesh Hamal", "Rishi Dhamala", "Salman Khan", "Shilpa Shetty", "Majnu Bhai", "Uday Shetty"]

override func viewDidLoad() {
    super.viewDidLoad()
    navigationItem.searchController = searchController
    tblUserList.register(UINib(nibName: "UserListCell", bundle: nil), forCellReuseIdentifier: "UserListCell")
    }
override func viewWillAppear(_ animated: Bool) {
    navigationController?.navigationBar.prefersLargeTitles = true
}

override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()
    self.constTableViewHeight?.constant = self.tblUserList.contentSize.height
}

@IBAction func btnAddUser(_ sender: UIButton) {
    let vc = UIStoryboard(name: "AddUser", bundle: nil).instantiateViewController(withIdentifier: "AddUser") as! AddUser
    navigationController?.pushViewController(vc, animated: true)
}

} '''

And this is the view controller that I am pushing to:

''' import UIKit import IBAnimatable

class AddUser: UIViewController, UIImagePickerControllerDelegate & UINavigationControllerDelegate {

@IBOutlet weak var imgProfilePicture: AnimatableImageView!
override func viewDidLoad() {
    super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
    navigationController?.navigationBar.prefersLargeTitles = false
}

@IBAction func btnChooseProfilePicture(_ sender: UIButton) {
    let alert = UIAlertController(title: "Choose Image", message: nil, preferredStyle: .actionSheet)
            alert.addAction(UIAlertAction(title: "Camera", style: .default, handler: { _ in
                self.openCamera()
            }))
            alert.addAction(UIAlertAction(title: "Gallery", style: .default, handler: { _ in
                self.openGallery()
            }))
            alert.addAction(UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil))

            self.present(alert, animated: true, completion: nil)
}

func openGallery()
{
    if UIImagePickerController.isSourceTypeAvailable(UIImagePickerController.SourceType.photoLibrary){
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.allowsEditing = true
        imagePicker.sourceType = UIImagePickerController.SourceType.photoLibrary
        self.present(imagePicker, animated: true, completion: nil)
    }
    else
    {
        let alert  = UIAlertController(title: "Warning", message: "You don't have permission to access gallery.", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
}
func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    if let pickedImage = info[.originalImage] as? UIImage {
        self.imgProfilePicture.image = pickedImage
    }
    picker.dismiss(animated: true, completion: nil)
}
func openCamera()
{
    if UIImagePickerController.isSourceTypeAvailable(UIImagePickerController.SourceType.camera) {
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.sourceType = UIImagePickerController.SourceType.camera
        imagePicker.allowsEditing = false
        self.present(imagePicker, animated: true, completion: nil)
    }
    else
    {
        let alert  = UIAlertController(title: "Warning", message: "You don't have camera", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
}

}

'''