title: Animation lags on device, but not in Simulator
body: <p>I want to trigger a <strong>CAAnimation</strong> with a Button. In playground and in the simulator, this works exactly as I want it to. However, when I run the same code on a device, the animation happens only after a short delay.</p>
  
  <p>Apparently, the issue only happens on iOS 11.2.6. I updated my device and can now not reproduce the issue anymore. Can anyone confirm, or find out, how it would work on iOS 11.2.6?</p>
  
  <pre><code>import UIKit
  
  class MyViewController : UIViewController {
      let animatedView = UIView()
  
      override func loadView() {
          let view = UIView()
          view.backgroundColor = .white
  
          // Add a button
          let button = UIButton(type: .system)
          button.frame = CGRect(x: 150, y: 200, width: 200, height: 50)
          button.setTitle("Animate", for: .normal)
          button.addTarget(self, action: #selector(tap), for: .touchUpInside)
  
          // Set color and frame of the view, that is animated.
          animatedView.backgroundColor = UIColor.blue
          animatedView.frame = CGRect(x: 50, y: 50, width: 50, height: 50)
  
          // Add the views to the view hierarchy
          view.addSubview(animatedView)
          view.addSubview(button)
          self.view = view
      }
  
      /// On Tap create an animation, that changes the position of the animated view.
      @objc func tap() {
          let originalY = animatedView.layer.position.y
          let animation = CABasicAnimation(keyPath: "position.y")
          animation.fromValue = originalY
          animation.toValue = 300.0
          animation.duration = 1.0
          animatedView.layer.add(animation, forKey: "positionAnimation")
      }
  }
  </code></pre>