Why video texture missing after playing video for the second time? and only play the audio

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI; using UnityEngine.Video;

public class StreamVideo : MonoBehaviour {

 public RawImage image;

 public VideoClip videoToPlay;

 private VideoPlayer videoPlayer;
 private VideoSource videoSource;

 private AudioSource audioSource;

 void Start () {
     Application.runInBackground = true;
     StartCoroutine(playVideo());
 }

 IEnumerator playVideo()
 {

     videoPlayer = gameObject.AddComponent<VideoPlayer>();

     audioSource = gameObject.AddComponent<AudioSource>();

     videoPlayer.playOnAwake = true;
     audioSource.playOnAwake = true;
     audioSource.Pause();

     videoPlayer.source = VideoSource.VideoClip;

     videoPlayer.audioOutputMode = VideoAudioOutputMode.AudioSource;

     videoPlayer.EnableAudioTrack(0, true);
     videoPlayer.SetTargetAudioSource(0, audioSource);

     videoPlayer.clip = videoToPlay;
     videoPlayer.Prepare();

     WaitForSeconds waitTime = new WaitForSeconds(1);
     while (!videoPlayer.isPrepared)
     {
         Debug.Log("Preparing Video");
         yield return waitTime;
         break;
     }


     Debug.Log("Done Preparing Video");

     image.texture = videoPlayer.texture;

     videoPlayer.Play();

     audioSource.Play();

     Debug.Log("Playing Video");
     while (videoPlayer.isPlaying)
     {
         Debug.LogWarning("Video Time: " + Mathf.FloorToInt((float)videoPlayer.time));
         yield return null;
     }
     Debug.Log("Done Playing Video");
 }

}

when i play video for the first time

and this when i back and touch the button for the second time to play video