TheDude recently upgraded the server to the most recent version of Lemmy. You'll notice significant improvements to the user interface, and hopefully the functionality is also improved. There is no official changelog yet because this version is not yet finalized, but I'll link the GitHub releases page where it should eventually appear.
https://github.com/LemmyNet/lemmy/releases
Edit: 0.18.1 is now fully released and we have upgraded to the final version. You can view the link above for the changelog.
Actually, hot and active seem to be much improved. I'm seeing popular posts from up to 2 days ago, but also mixed in with newer content.
I wasn't using those filters at all on 0.18.0, but I'll give them a shot now. I'll update this comment if I have any issues