How can I stop autoblog from reimporting old posts?

So over the past week or so, Autoblog has been taking a tour of old (in some cases, years old) posts from feeds that it monitors and re-importing them. This does not seem to be happening with every feed every time it is processed, but we're on a 24 hour refresh and it seems like every morning some feed or another has imported a mess of dozens of old posts that have already been imported.

The "Starting From" date in the feed processing settings is not being respected, either (that has also been happening in blogs that are just entered), so many posts published long before that day are being pulled in.