AVPlayerViewController controls not working - ios

Question

I have an app which plays video clips on demand. This has worked well in previous versions of Xcode but I've upgraded to 8.3.3 and am having problems with the AVPlayerViewController.
The video plays and displays correctly. The control bar appears at the bottom of the view but does not respond to taps and, once faded out, does not reappear on tapping the video - unless, that is, I tap near the top left of the view.
My guess is that the actual controls are hidden in some kind of overlay which has the wrong size i.e. it does not properly overlay the whole of the video view. Is there some way to force the AVPlayerViewController to relayout?
I've tried adding:
_playerController!.view.setNeedsLayout()
_playerController!.view.layoutIfNeeded()
But this has no effect.
Here's my code:
override func viewDidLoad() {
super.viewDidLoad()
_player = AVPlayer()
_playerController = AVPlayerViewController()
_playerController!.showsPlaybackControls = true
_playerController!.allowsPictureInPicturePlayback = false
_playerController!.videoGravity = AVLayerVideoGravityResizeAspectFill
_playerController!.player = _player
self.addChildViewController(_playerController!)
videoView.addSubview(_playerController!.view)
...
override func viewDidLayoutSubviews() {
let frame = UIScreen.main.bounds
_vidWidth = frame.width - 256.0
_vidHeight = _vidWidth / 854.0 * 480.0
videoView.frame = CGRect(x: 0, y: 10.0, width: _vidWidth, height: _vidHeight)
videoView.backgroundColor = UIColor.black
_playerController?.view.frame = CGRect(x: 0, y: 0, width: _vidWidth, height: _vidHeight)
...
func playVideo(_ clip: Clip) {
var videoUrl: URL? = nil
if clip.offlineLocation != nil && clip.state == 2 {
_videoPath = clip.offlineLocation!
videoUrl = URL(fileURLWithPath: _videoPath!)
}
else {
_videoPath = "https://xxxx.cloudfront.net/" + clip.location
videoUrl = URL(string: _videoPath!)
}
NSLog(_videoPath!)
let asset = AVURLAsset(url:videoUrl!, options:nil)
let playerItem = AVPlayerItem(asset: asset)
_player!.replaceCurrentItem(with: playerItem)
_player!.play()
}