title: Wordpress does not save Custom Field
body: <p>I am working with several Custom Fields which are "allocated" to Custom Post Types. For some odd reason one Custom Field needs to be created over and over again. I cannot seem to find a solution that this specific Custom Field is saved onto my Wordpress Database for future use.</p>
  
  <p>The Custom Field is called "video_url". Even if I rename it so "youtubelink" or whatsoever Wordpress does not save it. Any other newly created Custom Fields are saved by Wordpress but not that one that must hold the Youtube Link.</p>
  
  <p>Any ideas? Is there something to "force" WP to keep that Custom Field?</p>
  
  <p>NB: I am not using any Plugins to create Custom Fields.</p>