App crashes on iPad and iPhone running iOS 9.3.5 connected to an IPv6 network when we: - Pressed the Stop button

I tried to submit a sound app for ipad and phone. Then I was told that my play button would not play audio when pressed when connect to a ipv6. This was the code I used to start and stope the sound. It works how I intended when running the simulator.

import UIKit
import AVFoundation
class ViewController: UIViewController {
var audioPlayer = AVAudioPlayer()
var player1 = AVAudioPlayer()
func playsound(sender: AnyObject){

    let soundUrl = NSBundle.mainBundle().URLForResource("fsfa", withExtension: "mp3")! // or m4a

    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryAmbient)
        try AVAudioSession.sharedInstance().setActive(true)

        player1 = try AVAudioPlayer(contentsOfURL: soundUrl)
        player1.numberOfLoops = -1
        player1.prepareToPlay()
        player1.play()
    } catch _ {
        return print("sound file not found")
    }


}

func stopsound1(sender: AnyObject){
let soundUrl = NSBundle.mainBundle().URLForResource(“dsd”, withExtension: “mp3”)!
do {
try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryAmbient)
try AVAudioSession.sharedInstance().setActive(true)
player1 = try AVAudioPlayer(contentsOfURL: soundUrl)

        player1.stop()
    } catch _ {
        return print("sound file not found")
    }


}