Facebook social book mark

[the one]

So now i uploaded a thread to my facebook page from the social bookmark and it looks like this below.Why is it taking a copy of my banner logo.It does not matter how many threads i want to share to my facebook page its taking a copy of my forum logo.It did not used to do this it used to capture a picture from the thread.Is this something to do with the thumbnails i am confused lol

https://vborg.vbsupport.ru/external/2016/02/12.png

Many thanks