MapView Memory Leak ?

I have created a simple project with 2 view controllers. The first VC just has one button, that segue to the second VC. The second VC has an MKMapView and a back button.

I have put print statements into the VC lifecycle events to more easily track what is happening.

The problem is, when I return to the first VC, by hitting the back button in the second VC, a significant chunk of memory is not returned.

I have tried the memoryHotfix several other users indicated worked in earlier versions of Xcode - but this is not working - (changing mapView type, setting delegate and mapView to nil).

I can confirm the second VC is calling the deinit function (see debug trace)

@IBAction func btnShowMap(_ sender: UIBarButtonItem) {

     print("********* MainVC \(#function) **********")

     performSegue(withIdentifier: "showMap", sender: nil) self.dismiss(animated: true, completion: {})

}

override func viewDidLoad() {

     print("********* MainVC \(#function) **********")

     super.viewDidLoad()

}

override func didReceiveMemoryWarning()

print("********* MainVC \(#function) **********")

     super.didReceiveMemoryWarning()

}

override func viewWillDisappear(_ animated: Bool)

print ("********* MainVC \(#function) ********** ")

}

override func viewDidDisappear(_ animated: Bool) {

print ("********* MainVC \(#function) ********** ")

}

override func viewDidAppear(_ animated: Bool) {

print ("********* MainVC \(#function) ********** ")

}

override func viewWillAppear(_ animated: Bool) {

print ("********* MainVC \(#function) ********** ")

}

deinit {

print ("********* MainVC \(#function) ********** ")

}

here is the code for the second (Map) VC -

class MapVC: UIViewController, MKMapViewDelegate {

@IBOutlet weak var mapView: MKMapView!

@IBAction func btnBack(_ sender: UIButton) {

     self.dismiss(animated: true, completion: {})

}

override func viewDidLoad() {

     print("********* MapVC \(#function) **********")

     super.viewDidLoad()

     print (" mapView.delegate = self")

     self.mapView.delegate = self

}

override func didReceiveMemoryWarning() {

     print("********* MapVC \(#function) **********")

     super.didReceiveMemoryWarning()

}

func removeNastyMapMemory() {

     print (" ********* MapVC \(#function) ********** ")

     if mapView != nil {

          switch mapView.mapType {

          case .hybrid :

               print (" mapType = MKMapType.standard")

               mapView.mapType = MKMapType.standard

          case .standard:

               print (" mapType = MKMapType.hybrid")

               mapView.mapType = MKMapType.hybrid

          default:

               print (" mapType = ???")

               break

          }

          print (" showsUserLocation = false")

          mapView.showsUserLocation = false

          if mapView.delegate != nil {

               print (" mapView.delegate = nil")

               mapView.delegate = nil

          }

          print (" mapView = nil")

          mapView.removeFromSuperview() mapView = nil

     }

}

override func viewWillDisappear(_ animated: Bool) {

     print ("********* MapVC \(#function) ********** ")

     removeNastyMapMemory()

}

override func viewDidDisappear(_ animated: Bool) {

     print ("********* MapVC \(#function) ********** ")

}

override func viewDidAppear(_ animated: Bool) {

     print ("********* MapVC \(#function) ********** ")

}

override func viewWillAppear(_ animated: Bool) {

     print ("********* MapVC \(#function) ********** ")

}

deinit {

     print ("********* MapVC \(#function) ********** ")

}

here is the output debug trace -

********* MainVC viewDidLoad() **********

********* MainVC viewWillAppear **********

********* MainVC viewDidAppear **********

********* MapVC viewDidLoad() **********

mapView.delegate = self

********* MainVC viewWillDisappear **********

********* MapVC viewWillAppear **********

********* MapVC viewDidAppear **********

********* MainVC viewDidDisappear **********

********* MapVC viewWillDisappear **********

********* MapVC removeNastyMapMemory() **********

mapType = MKMapType.hybrid

showsUserLocation = false

mapView.delegate = nil

mapView = nil

********* MainVC viewWillAppear **********

********* MainVC viewDidAppear **********

********* MapVC viewDidDisappear **********

********* MapVC deinit **********

********* MapVC viewDidLoad() **********

mapView.delegate = self

********* MainVC viewWillDisappear **********

********* MapVC viewWillAppear **********

********* MapVC viewDidAppear **********

********* MainVC viewDidDisappear **********

********* MapVC viewWillDisappear **********

********* MapVC removeNastyMapMemory() **********

mapType = MKMapType.hybrid

showsUserLocation = false

mapView.delegate = nil

mapView = nil

********* MainVC viewWillAppear **********

********* MainVC viewDidAppear **********

....this continues as many times as you push the Map and Back buttons

and here is the memory usage just keeps going up and up.

Am I missing something here - or doing something wrong ?

Or is this a memory leak and I should raise a radar ?

Any help appreciated

Info :

Xcode Version 8.3 beta (8W109m)

Mac OS Sierra Version 10.12.3