Hi there!
I would like to report two issues and ask for a patch. The weird thing is that before I did not have similar problems, something might have happened to the Facebook API, or I don't know. Worth to mention that no updates were installed, and no background settings were changed in Joomla recently which might have affected the functionality.
1. When posting an article the plugin simply ignores the "Read more" sign and tries to load the full K2 article text into facebook (until the character limit is reached of course). I would expect the plugin to load only the text before the "Read more" sign.
2. When I create a K2 article from scratch and click the checkbox to post in on facebook, then hit save, a broken link is posted on facebook with no text and image. BUT... if I first save the article, then open it for editing and click the facebook checkbox, then save again the article is posted fine on facebook.
3. This is related to issue #2. If I edit an article (article name or text) and would like to re-post on facebook, the old article name and text will be posted.
Could you please have a look at these issues?