Losing access to DOM after initizing player? Errrm WHY? (Projekktor Core)

I dont know how to explain this problem other than by example. When you click on "File 1" OR File 2, it always works on the first click. But if you click the other link at any point, whether the video is playing, paused, or stopped, it simply will not run because it's getting an error from the DOM.

I am trying to do a very simple HREF based playlist. Something this simple seems like it would just work, but it does not.

Please do not tell me how to use the playlist. I am not interested in using that for this particular issue. I simply want to know why I cannot access the DOM. If it's renamed or whatever, I need to know what it's renamed to, or if it's accessed differently, I need to know that too.

This is NOT the actual install I will be using. This is only to demonstrate the DOM issue I'm having with a player that DOES have a playlist. This is the simplest example I could write that demonstrates the problem at hand. If someone could take this code and make it work, that would be awesome. I could then take the methods and apply it to my other install.

The error I get is:
Uncaught TypeError: Cannot read property 'src' of null

<link rel="stylesheet" href="style.css" type="text/css" media="screen" />
<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript" src="projekktor.min.js"></script> <!-- load projekktor -->

<a href=# onClick='write_filepath("bbb_trailer_mobile.m4v");'>File 1</a>
<a href=# onClick="write_filepath('sintel-trailer.m4v');">File 2</a>

<video id=player_a class="projekktor" poster="" title="This is Projekktor" width="640" height="385" controls id="player_a">
<source id=dummy src="#DummyEntry" />
</video>

<script>
function write_filepath(filepath)
{
   alert(filepath);
   alert(document.getElementById('dummy').src);
   document.getElementById('dummy').src=filepath;
   alert(document.getElementById('dummy').src);
   projekktor('#player_a', {});
   return;
}
</script>