I have the same error it has to do with the image that should be provided as og:image.
The code that figures out the image dimensions for some images throws a Fatal Error.
If you comment out line 834 in file class-webdados-fb-open-graph-public.php it works again.
Background:
The plugin tries to get the image size by only loading a small part of the image for speed reasons but this gives the Fatal Error. I think it was(?) only a warning in other PHP Versions that should not stop the script, but the Fatal Error does, hence the HTML is truncated.
In Line 834 is where the script asks for only a part of the image file, commenting it out tells the script to load the whole image and then in works.