Audio won't play after app interrupted by phone call iOS

I have a problem in my SpriteKit game where audio using playSoundFileNamed(_ soundFile:, waitForCompletion:) will not play after the app is interrupted by a phone call. (I also use SKAudioNodes in my app which aren't affected but I really really really want to be able to use the SKAction playSoundFileNamed as well.)

Here's the gameScene.swift file from a stripped down SpriteKit game template which reproduces the problem. You just need to add an audio file to the project and call it "note"

I've attached the code that should reside in appDelegate to a toggle on/off button to simulate the phone call interruption.

That code 1) Stops AudioEngine then deactivates AVAudioSession - (normally in applicationWillResignActive) ... and 2) Activates AVAudioSession then Starts AudioEngine - (normally in applicationDidBecomeActive)

The error:

AVAudioSession.mm:1079:-[AVAudioSession setActive:withOptions:error:]: Deactivating an audio session that has running I/O. All I/O should be stopped or paused prior to deactivating the audio session.

This occurs when attempting to deactivate the audio session but only after a sound has been played at least once. to reproduce:

1) Run the app 2) toggle the engine off and on a few times. No error will occur. 3) Tap the playSoundFileNamed button 1 or more times to play the sound. 4) Wait for sound to stop 5) Wait some more to be sure

6) Tap Toggle Audio Engine button to stop the audioEngine and deactivate session - the error occurs.

7) Toggle the engine on and of a few times to see session activated, session deactivated, session activated printed in debug area - i.e. no errors reported.

8) Now with session active and engine running, playSoundFileNamed button will not play the sound anymore.

What am I doing wrong?

p.s. I also tried self.removeAllActions() before deactivating but it didn't help.

import SpriteKit
import AVFoundation

class GameScene: SKScene {
  var toggleAudioButton: SKLabelNode?
  var playSoundFileButton: SKLabelNode?
  var engineIsRunning = true

  override func didMove(to view: SKView) {
    toggleAudioButton = SKLabelNode(text: "toggle Audio Engine")
    toggleAudioButton?.position = CGPoint(x:20, y:100)
    toggleAudioButton?.name = "toggleAudioEngine"
    toggleAudioButton?.fontSize = 80
    addChild(toggleAudioButton!) 
   
    playSoundFileButton = SKLabelNode(text: "playSoundFileNamed")
    playSoundFileButton?.position = CGPoint(x: (toggleAudioButton?.frame.midX)!, y: (toggleAudioButton?.frame.midY)!-240)
    playSoundFileButton?.name = "playSoundFileNamed"
    playSoundFileButton?.fontSize = 80
    addChild(playSoundFileButton!)
  }

  override func touchesBegan(_ touches: Set, with event: UIEvent?) {
    if let touch = touches.first {
      let  location = touch.location(in: self)
      let  nodes = self.nodes(at: location)
     
      for spriteNode in nodes {
        if spriteNode.name == "toggleAudioEngine" {
          if engineIsRunning { // 1 stop engine, 2 deactivate session

            scene?.audioEngine.stop() // 1
            toggleAudioButton!.text = "engine is paused"
            engineIsRunning = !engineIsRunning
            do{
              // this is the line that fails when hit anytime after the playSoundFileButton has played a sound
              try AVAudioSession.sharedInstance().setActive(false) // 2
              print("session deactivated")
            }
            catch{
              print("DEACTIVATE SESSION FAILED")
            }
          }
          else { // 1 activate session/ 2 start engine
            do{
              try AVAudioSession.sharedInstance().setActive(true) // 1
              print("session activated")
            }
            catch{
              print("couldn't setActive = true")
            }
            do {
              try scene?.audioEngine.start() // 2
              toggleAudioButton!.text = "engine is running"
              engineIsRunning = !engineIsRunning
            }
            catch {
              //
            }
          }
        }
       
        if spriteNode.name == "playSoundFileNamed" {
          self.run(SKAction.playSoundFileNamed("note", waitForCompletion: false))
        }
      }
    }
  }
}