Thank for this fix. I will now post it as a comment for translation editor.

;-)

I've posted a link to here on the translation editor plugin page: http://community.elgg.org/pg/plugins/release/461373/developer/jeabakker/translation-editor

it shows a nother solution that you may want to consider. 

In any case, I'd be happy to read ou conclusions :)

Thank you iZAP,  here is the working solution for your next update

The best solutions so far is to move

function video_echo($key) {
  return elgg_echo('izap_videos:' . $key);
}

from izap_videos/languages/en.php to izap_videos/start.php.

This fix was kindly provided by Jerome: http://community.elgg.org/pg/plugins/release/461373/developer/jeabakker/translation-editor

Blessings