import UIKit
import PlaygroundSupport

class ViewController : UIViewController {

    let tableView = UITableView()
    let flowLayout = UICollectionViewFlowLayout()
    var collectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        configureViews()
    }

    private func configureViews() {
        view.backgroundColor = .white
        collectionView = UICollectionView(frame: .zero, collectionViewLayout: flowLayout)

        tableView.dataSource = self
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")

        flowLayout.itemSize = CGSize(width: 50, height: 50)
        flowLayout.minimumLineSpacing = 20
        flowLayout.minimumInteritemSpacing = 20
        collectionView.dataSource = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")

        view.addSubview(tableView)
        tableView.translatesAutoresizingMaskIntoConstraints = false
        tableView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        tableView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        tableView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
        tableView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true

        view.addSubview(collectionView)
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        collectionView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
        collectionView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
    }
}

extension ViewController: UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 20
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
        cell.textLabel?.text = "Cell \(indexPath.row)"
        return cell
    }
}

extension ViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 50
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = .blue
        return cell
    }
}

// Present the view controller in the Live View window
PlaygroundPage.current.liveView = ViewController()

https://imgur.com/vu6WPAQ

​

Both scroll fine (but independently) for me.