Code works in editor, but not on Android device(audio mixer)

Hey have created a script which should make a transition between two audio mixer groups and it works fine if I test it in the editor: the first groups volume decreases and the other groups volume increases. After the transition the volumes don't change in the editor, but if I run my game on my HTC One M9 the transition works and after it the first groups volume jumps to 100% although it should be 0.

The Coroutine which makes the transition is the changeChannel IEnumerator at the bottom of the script.

If you need an example you can download https://www.dropbox.com/s/riwis1zj4utjb9l/Android%20sound%20test.zip?dl=0, this is an example project using the code below.

Do you know why it doesn't work?

 using UnityEngine;
 using System.Collections;
 using UnityEngine.Audio;
 
 public class AudioScr : MonoBehaviour {
     public AudioMixer masterMixer;
     public float changeMusicChannelTime;
     private float lastPitch=0, currentPitch,currentTime,progress;
     // Use this for initialization
     void Start () {
         masterMixer.SetFloat ("MmusicVol", 0);
         masterMixer.SetFloat ("IGmusicVol", -50);
     }
     
     // Update is called once per frame
     void Update () {
         currentPitch = Time.timeScale;
         if (currentPitch != lastPitch) {
             masterMixer.SetFloat ("IngameMusicPitch", currentPitch);
         }
         if (currentPitch == 0 && lastPitch != 0) {
             
             StartCoroutine (changeChannel (false));
         } else if (currentPitch != 0 && lastPitch == 0) {
             
             StartCoroutine (changeChannel (true));
         }
         lastPitch = currentPitch;
     }
 
     public void changeChannelTimeAdjust(float newTime){
         changeMusicChannelTime = newTime * 5+0.1f;
     }
 
     public void SetEffectVolume(float effectVol){
         if (effectVol != 0) {
             effectVol = 20 * Mathf.Log10 (effectVol);
         } else {
             effectVol = -50;
         }
         masterMixer.SetFloat ("effectVolume", effectVol);
     }
 
     public void SetMusicVolume(float musicVol){
         if (musicVol != 0) {
             musicVol = 20 * Mathf.Log10 (musicVol);
         } else {
             musicVol = -50;
         }
 
         
         masterMixer.SetFloat ("musicVolume", musicVol);
     }
 
     IEnumerator changeChannel(bool purpose){
         Debug.Log ("Start channel switch: "+purpose);
         do{
             currentTime += Time.unscaledDeltaTime;
 
             progress = currentTime / changeMusicChannelTime;
 
             if (purpose) {
                 //from Menue to Ingame
                 float MmusicVol = 20 * Mathf.Log10 (1-progress);
                 float IGmusicVol = 20 * Mathf.Log10 (progress);
                 if (progress == 0) {
                     IGmusicVol = -50;
                 } else if (progress == 1) {
                     MmusicVol = -50;
                 }
 
                 masterMixer.SetFloat ("MmusicVol", MmusicVol);
                 masterMixer.SetFloat ("IGmusicVol", IGmusicVol);
             } else {
                 //from Ingame to Menue
                 float MmusicVol = 20 * Mathf.Log10 (progress);
                 float IGmusicVol = 20 * Mathf.Log10 (1 - progress);
                 if (progress == 0) {
                     MmusicVol = -50;
                 }else if (progress == 1) {
                     IGmusicVol = -50;
                 }
 
                 masterMixer.SetFloat ("MmusicVol", MmusicVol);
                 masterMixer.SetFloat ("IGmusicVol", IGmusicVol);
             }
             yield return null;
         }while (progress < 1);
         progress = 0;
         currentTime = 0;
 
 
     }
             
 
 
 
 }