I sent a note about this to Support, and here's what they said:
It looks like Facebook changed their URL structure a bit for data returned from their API. For your page, we used to get entries with URLs like:?
Yesterday, it appears they switched to using your pageid instead. The same entry now comes back as:
We use the URL as a key indicator whether an entry is new or not. Perhaps I need to look into a secondary indicator, such as a hash.
Dana Todd