I have a share button that has been working for months. Today (May 12, 2015) I start receiving calls that the share button is pulling the wrong image. The odd thing is that some pages it pulls the right image, other pages it doesn't. When it doesn't pull the right image, it is pulling one from another completely different page. Even when the image is incorrect, if you continue it will post the share using the correct image.
I went and verified the OG meta data. I received a warning about the og:image. The strange thing is that right after the warning is displayed, the og:image information is shown and it was correct and the image it display on the verification page was correct. The image size is greater that 200x200, is accessible to facebook and is a jpg.
Just to make this a little bit more interesting. It appears the first few times you hit the share button it works. Then at some point it stops using the correct image.
Here is an example: http://www.houseviewonline.com/Real-Estate-Listing.php?ID=27111