Leading Swipe action in UIPageViewController is not working when it is pushed on UINavigationController.

When a UIPageViewController is pushed in a UINavigationController, the leading swipe action from middle of screen dismisses the PageViewController instead of going to previous page.

When the Example code is opened from Xcode 16.4.0,

• ✅ Left Swipe action from left screen edge of screen dismisses the Page View Controller.
• ✅ Left Swipe action from middle of screen goes to previous Page in Page View Controller

When the Example code is opened from Xcode 26.0 - Beta 6,

• ✅ Left Swipe action from left screen edge of screen dismisses the Page View Controller.
• ❌ Left Swipe action from middle of screen sometimes goes to previous page and sometimes dismisses the Page View Controller.

Example code that the issue occurs:

import Foundation
import UIKit
import PlaygroundSupport

PlaygroundPage.current.setLiveView(
    UINavigationController(rootViewController: RootViewController())
)

class RootViewController: UIViewController {
    lazy var pageVCButton: UIButton = {
        let button = UIButton()
        button.setTitle("Open Page VC", for: .normal)
        button.setTitleColor(.label, for: .normal)
        button.addAction(UIAction(handler: { [weak self] _ in
            self?.didTapPageVCButton()
        }), for: .touchUpInside)
        return button
    }()
    
    lazy var pageContainerViewController = PageContainerViewController(startIndex: 3)
    
    func didTapPageVCButton() {
        print("didTapPageVCButton")
        navigationController?.pushViewController(pageContainerViewController, animated: true)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground
        
        addOpenPageVCButton()
    }
    
    private func addOpenPageVCButton() {
        view.addSubview(pageVCButton)
        pageVCButton.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            pageVCButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            pageVCButton.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        ])
    }
}

class PageContainerViewController: UIViewController {
    lazy var pageViewController: UIPageViewController = {
        let pageViewController = UIPageViewController(
            transitionStyle: .scroll,
            navigationOrientation: .horizontal,
            options: nil
        )
        pageViewController.dataSource = self
        pageViewController.delegate = self
        return pageViewController
    }()
    
    lazy var pages: [ColouredViewController] = [
        ColouredViewController(backgroundColor: .red),
        ColouredViewController(backgroundColor: .blue),
        ColouredViewController(backgroundColor: .green),
        ColouredViewController(backgroundColor: .yellow),
        ColouredViewController(backgroundColor: .brown),
        ColouredViewController(backgroundColor: .link),
        ColouredViewController(backgroundColor: .cyan),
    ]
    
    var startIndex = 0
    
    init(startIndex: Int) {
        super.init(nibName: nil, bundle: nil)
        self.startIndex = startIndex
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        navigationController?.title = "Page View Controller"
        print(pageViewController.gestureRecognizers)
        
        setupPageViewController()
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    }
    
    private func setupPageViewController() {
        addChild(pageViewController)
        view.addSubview(pageViewController.view)
        pageViewController.didMove(toParent: self)
        
        pageViewController.view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            pageViewController.view.topAnchor.constraint(equalTo: view.topAnchor),
            pageViewController.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            pageViewController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            pageViewController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        ])
        
        pageViewController.setViewControllers([pages[startIndex]], direction: .forward, animated: true)
    }
}

extension PageContainerViewController: UIPageViewControllerDataSource {
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        print("Leading Swipe")
        guard let viewController = viewController as? ColouredViewController else { return nil }
        guard let currentPageIndex = pages.firstIndex(of: viewController) else { return nil }
        if currentPageIndex == 0 { return nil }
        return pages[currentPageIndex - 1]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        print("Trailing Swipe")
        guard let viewController = viewController as? ColouredViewController else { return nil }
        guard let currentPageIndex = pages.firstIndex(of: viewController) else { return nil }
        if currentPageIndex == pages.count - 1 { return nil }
        return pages[currentPageIndex + 1]
    }
}

extension PageContainerViewController: UIPageViewControllerDelegate {}

class ColouredViewController: UIViewController {
    var backgroundColor: UIColor?
    
    init(backgroundColor: UIColor) {
        super.init(nibName: nil, bundle: nil)
        self.backgroundColor = backgroundColor
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = backgroundColor
    }
}