Running YTE 2.5.6 on the latest WP and mostly default options. A couple small things came up I wanted to share.
One of the YT videos has double dashes in the ID: yIW--5LiN0k
If I copy/paste the entire "Share" link in the shortcode an error occurs. The page source shows:
!-- YouTube Embed v2.5.6 | http://www.artiss.co.uk/artiss-youtube-embed --> <!-- The YouTube ID of yIW is invalid. --> <p>The video cannot be shown at the moment. Please try again later.</p> <!-- End of YouTube Embed code -->
If I remove the link from the shortcode and just use the ID the video thumb displays fine. While it's more convenient to just copy/paste the entire "Share" link, trimming this down to just ID is an easy work-around.
The second thing was trying to style that particular error message so it would take up the same space of the default video thumb size and not mess up the layout. I tried to add a class selector in the Error Reporting Options, e.g.
<p class="error"> but after Save Settings I see backslashes on the quotes, which causes the code to be invalid and any CSS ignored.
I tried doing the above on a different WP site with a different template and got the same results so they seem to be core plugin issues. Not major, but should not occur. Otherwise, an excellent plugin.