Youtube iframe api not triggering onYouTubeIframeAPIReady-Collection of common programming errors

I’ve been battling with the youtube iframe api for quite some time now. Somehow the method onYouTubeIframeAPIReady is not always triggered.

From the symptoms it seems a loading problem. No errors are shown in the inspector.

Here is my code:

html

          
            videoId = 'someVideoId';
            var tag = document.createElement('script');
            tag.src = "//www.youtube.com/iframe_api";
            var firstScriptTag = document.getElementsByTagName('script')[0];
            firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);
          

js (called at the end of the page. I tried to place the code right after the above script and the result was the same.)

var isReady = false
  , player
  , poster
  , video;

$(function () {
$('.js-play').click(function (e) {
    e.preventDefault();
    interval = setInterval(videoLoaded, 100);
  });
});
function onYouTubeIframeAPIReady() {
  console.log(videoId)
  player = new YT.Player('player', {
    height: '445',
    width: '810',
    videoId: videoId,
    events: {
      'onReady': onPlayerReady//,
      //'onStateChange': onPlayerStateChange
    }
  });
}

function onPlayerReady(event) {
  isReady = true;
  console.log("youtube says play")
}

function videoLoaded (){
  if (isReady) {
      console.log("ready and play")
      poster.hide();
      video.show();

      $('body').trigger('fluidvideos');

      player.playVideo();
      clearInterval(interval);
  } 
}

The problem is that sometimes nothing gets printed by the console.log and nothing happens.

On mobile phones this happens all the time. Any ideas?