When calling a Twitter API such as
it turns out that Twitter sometimes responds with a string like:
Couldn't find Status with ID=891433567
instead of an actual JSON object.
Unfortunately this breaks the JSON::Any->jsonToObj( $req->content ) that's the punchline to most Net::Twitter methods. So while there might be 98 or 99 good status messages, Net::Twitter::friends_timeline() e.g. silently returns undef, as though no new tweets were available.