Facebook og: image not working correctly now?

A few days ago, incorrect images started showing up in Facebook posts during posting, although the pages that were posted have the correct og: image tag pointing to large enough images.

Does anyone know what the problem is? Could it have something to do with recent API updates?

Examples:

1) http://bigpicture.ru/?p=633696 - OG Object Debugger shows: "og: image is not defined, cannot be loaded or is not large enough" warning. The page has:

<meta property="og:image" 
content="http://bigpicture.ru/wp-content/uploads/2015/05/Jpsportcars19-800x440.jpg"/>
      

        
        
        
      

    

which is large enough.

2) http://postila.ru/post/26862259 - the debugger gives the same warning. Again, the page has the correct og: image tag, the image is large enough. During the manual posting, we see that Facebook is taking the wrong picture, one of the small photos presented on the page.

Any ideas on what's going on with Facebook today and how to fix it?