SWIFT UIPanGestureRecognizer failed only first time - swift

Question

My test app have 4 ScrollView.
UIScrollView which can scroll up/down.
UIPageViewController inside 1, which can scroll left/right.
UITableView inside one of viewController 2, can scroll up/down.
UIScrollView inside UITableViewCell on tableView 3, can scroll left/right.
https://i.stack.imgur.com/BexX3.jpg
First swipe gesture by UIScrollView 4 causes PageViewController 2 scroll instead. Second and more swipes work correct.
PanGestureRecognizer of UIScrollView 4 has a state "failed" on the first swipe.
<UIScrollViewPanGestureRecognizer: 0x7f826881fd50; state = Failed; delaysTouchesEnded = NO; view = <Tests.MyCellScroll 0x7f826802f600>; target= <(action=handlePan:, target=<Tests.MyCellScroll 0x7f826802f600>)>>
Any ideas what’s the problem or how could it be debugged?
Example
class ViewController: UIViewController {
private let vcs: [UIViewController] = [
MyVC(),
UIViewController()
]
private lazy var scroll: UIScrollView = {
let scroll = UIScrollView()
scroll.backgroundColor = .systemPink
return scroll
}()
private lazy var pageVC: UIPageViewController = {
let page = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
page.view.backgroundColor = .white
page.delegate = self
page.dataSource = self
return page
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(self.scroll)
self.addChild(self.pageVC)
self.scroll.addSubview(self.pageVC.view)
self.pageVC.didMove(toParent: self)
self.pageVC.setViewControllers([self.vcs[0]], direction: .forward, animated: true, completion: nil)
}
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
self.scroll.frame = self.view.frame
self.scroll.contentSize = CGSize(width: self.view.frame.width, height: self.view.frame.height + 50)
self.pageVC.view.frame = CGRect(x: self.scroll.bounds.minX, y: self.scroll.bounds.minY + 250, width: self.scroll.bounds.width, height: self.scroll.contentSize.height - 250)
}
}
extension ViewController: UIPageViewControllerDataSource, UIPageViewControllerDelegate {
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
self.vcs.firstIndex(of: viewController) == 1 ? self.vcs[0] : nil
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
self.vcs.firstIndex(of: viewController) == 0 ? self.vcs[1] : nil
}
}
final class MyVC: UIViewController {
private lazy var table: UITableView = {
let table = UITableView()
table.register(MyCell.self, forCellReuseIdentifier: String(describing: MyCell.self))
table.delegate = self
table.dataSource = self
return table
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(self.table)
}
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
self.table.frame = self.view.frame
}
}
extension MyVC: UITableViewDelegate, UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 5 }
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { MyCell() }
}
final class MyCell: UITableViewCell {
private lazy var subview: UIView = {
let view = UIView()
view.backgroundColor = UIColor.systemBlue.withAlphaComponent(0.7)
return view
}()
private lazy var scrollView: MyCellScroll = {
let view = MyCellScroll()
return view
}()
init(){
super.init(style: .default, reuseIdentifier: nil)
self.contentView.backgroundColor = UIColor.systemOrange.withAlphaComponent(0.7)
self.contentView.addSubview(self.scrollView)
self.scrollView.addSubview(self.subview)
}
override func layoutSubviews() {
super.layoutSubviews()
let frame = self.contentView.frame
self.scrollView.frame = frame
self.scrollView.contentSize = CGSize(width: 500, height: frame.height)
self.subview.frame = CGRect(x: 16, y: 8, width: 500 - 32, height: frame.height - 16)
}
required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
}
final class MyCellScroll: UIScrollView, UIGestureRecognizerDelegate {
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
print(gestureRecognizer)
return false // 5
}
}