Title posted instead of teaser to fb

First: I've done everything, which was mentioned in the header of new issue submitting page.

My problem is, that when I post a node to Facebook, the node title get posted twice, and the first image, but not the teaser of the node. When I commented or liked the same node, the resulted post in my timeline at Facebook do contained the teaser of the node correctly.

I checked the followings:
- https://developers.facebook.com/tools/debug/ shows every OG tag is correct and found no problem on the page
- manual checking also clearly shows there is og:description tag in the header of the page, and the value of this tag is the node teaser
- Facebook Devel modul generates this notices in the log:

Notice: Undefined variable: app fb_post_entity_page() függvényben (/var/www/html/phgimnazium-dev.drupler.hu/sites/all/modules/fb/fb_post.module 98 sor).

Notice: Undefined variable: node fb_post_entity_page() függvényben (/var/www/html/phgimnazium-dev.drupler.hu/sites/all/modules/fb/fb_post.module 93 sor).

I've attached the two different state of the Facebook posts:
- first shows the "shared" state of the node: title, field image and node teaser displays correctly
- second show the "posted" state of the node: title and field image are correct, but instead of the node teaser node title displayed

I'm looking for any direction to investigate. At the moment, I'm totally bumped and clueless...