When sharing a photo, photo album or a post, Facebook delivers the following message ...
This content is no longer available
The content you requested cannot be displayed right now. It may be temporarily unavailable, the link you clicked on may have expired, or you may not have permission to view this page.
Usually, the message expected would be a confirmation message that says the message has been successfully shared.
In fact, even though the message says the content is not available, it has been successfully shared.
Some people are likely to make several attempts after getting the failure message. Instead they end up posting the "share" several times.