Geeklog Forums

I've read some posts with problems of feeds not updating, I seem to have the opposite problem. Even with no new posts, no changes to a story, or any admin-related syndication modifications, the feeds seem to update and send old stories/forum topics as new randomly. Sometimes it's a topic with all it's existing old stories coming in as 'new', other time it's just 1 or 2 existing stories within a topic, or the forum that 'rings the bell'. Certainly not a major issue, more of a curiosity as to what would cause it.