Animation lags on device, but not in Simulator - swift

Question

I want to trigger a CAAnimation 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.
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?
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")
}
}

Answer 1

Can you try this code with iOS 11.2.9, I have tested your code and it's working fine.
// MARK: Animations
public extension CALayer {
var ani: CAAnimation {
let startPointAnim = CABasicAnimation(keyPath: #keyPath(CAGradientLayer.startPoint))
startPointAnim.fromValue = CGPoint(x: 0, y: 0.0)
startPointAnim.toValue = CGPoint(x:0, y: 300)
let endPointAnim = CABasicAnimation(keyPath: #keyPath(CAGradientLayer.endPoint))
endPointAnim.fromValue = CGPoint(x: 0, y: 0)
endPointAnim.toValue = CGPoint(x:2, y: 300)
let animGroup = CAAnimationGroup()
animGroup.animations = [startPointAnim, endPointAnim]
animGroup.duration = 1.0
animGroup.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
return animGroup
}
func playAnimation(_ anim: SkeletonLayerAnimation, key: String) {
recursiveSearch(inArray: skeletonSublayers,
leafBlock: { add(anim(self), forKey: key) }) {
$0.playAnimation(anim, key: key)
}
}
func stopAnimation(forKey key: String) {
recursiveSearch(inArray: skeletonSublayers,
leafBlock: { removeAnimation(forKey: key) }) {
$0.stopAnimation(forKey: key)
}
}
}