Well, I also had problems with facebook, like plugins, and also heard from people that this is a facebook bug. After a lot of searching on gOOgle .... I found a good result and I don't think this is a fb error.
You will need to add this file to your website header:
<meta property="og:image" content="http://ia.media-imdb.com/images/rock.jpg" />
Property of meta tags (facebook likes meta tags) ==> og: image - URL of the image that your object should represent inside the chart.
Replace "http://ia.media-imdb.com/images/rock.jpg" with the real path to the image.
For Wordpress Users
Add the following header to the header of your header file ==>
<?php $img= get_post_meta($post->ID, 'image', true); if ($img): ?> <meta property="og:image" content="<?=$img ?>"/> <? endif; ?>
That's all ... I hope this works for you all !! Share your experience ...
source share