If a file will not play back there are many possible reasons, one if them is that the file is a "broken file." Look at the following link.


The part of the url that says "brokenfile" indicates that the file referred to in the database does not exist in Moodle. 

The part that says "user/draft" is the most worrying, this indicates a temporary link that is used in html editor text areas. The file referred to in a user/draft link is only available in the text area it was uploaded to. Moodle does magic when the text area contents are submitted, to save the file and link and rewrite the link.  


So possibly the link has been copied and pasted from one text area to another and saved. The original file then will not be found when the text area contents are saved, and we get a broken link.