I am trying to implement group video functionality and I have following code

class App extends Component {
  this.state = {
     subscribers: [],
     subscriberVideos: [],
     screenVideo: undefined,
     publisherVideo: undefined,
     publisher: undefined,
  }
}

async start() {
  let publisher = OT.initPublisher(null, this.defaultPublisherProps, error => {
    if(error) {
    }  
  })
 publisher.on('videoElementCreated', this.onPublisherVideoElement);
 this.state.otSession.publish(publisher, error => {
    if (error) {
   }
   this.setState(() => {
     return { publisher: publisher };
   }
  }
}

onPublisherVideoElement = event {
  this.setState(() => {
   return { publisherVideo: event.element }
   });
  }
}

onPublisherScreenElement = event => {
  this.setState(() => {
    return { screenVideo: event.element }
 }
}

onSubscriberVideoElement = event => {
   this.setState(() => {
      return { 
        subscriberVideos: [...this.state.subscriberVideos, event.element]
      }
     }
   })
}

onSessionStreamCreated = event => {
  let subscriber = this.state.otSession.subscriber(event.stream, null, this.defaultSubscriberProps, error => {
     if (error) {
     }
    if (event.stream.videoType == 'screen') {
      subscriber.on('videoElementCreated', this.onPublisherScreenElement);
      this.setState(() => {
        return { screenSubscriber: subscriber };
      })
   } else {
     subscriber.on('videoElementCreated', this.onSubscriberVideoElement);
       if (this.props.mdm === "m") {
          this.setState((prevState) => {
             return {
               subscribers: [...this.state.subscribers, subscriber]
             }
          }
        }
     else {
       return { subscribers: [...this.state.subscribers, subscriber] }
     }
   }
  }
}

While showing subscribers I am doing

showSubscribers() {
    return this.state.subscribers.filter(subscriber => subscriber.stream !== null).map((subscriber, index) => {
       return(
          <VideoSubscriber
             key={index}
             otok={this.otok}
             subscriber={this.state.subscribers[index]
             subscriberVidoe={this.state.subscriberVideos[index]
            />
       )
    }
}

But at random times the video goes black and also while some of the subscriber refresh the page it goes blank creates multiple subscirber with null stream.
How can i resolve this?