I have an Activity Stream gadget set up in one of my dashboards that I use to review activity from previous days. This morning, however, I was only able to click on "Show more" twice before this warning appeared and prevented me from loading more entries.

Barely the last hour of the previous day's activity had loaded. I'm certain I've been using this gadget for more than half a year, but I would also expect that each time the gadget loads it fetches records from a database ordered by the newest first, so unless I'm misunderstanding something this seems to be a bug.
Interestingly, if I add a new activity stream gadget, it works fine and can seemingly load indefinitely. As soon as I apply a user ID filter, however, the above issue occurs.