[Plugin – Related Post by Zemanta] Default thumbnail is showing

I embedded the youtube / Vimeo videos in a post and installed “Video Plugin” to generate thumbnails from the video. In the homepage it is working fine but in related posts, it shows the default images in some thumbnail post and in some it shows the actual thumbnail generated from video. Plz help me to resolve it .

You can check the test link at
https://bsssphoto.com/blog/?p=484