I'm not sure if that's only on Reddthat and 0.18 servers (I'll go check out my account on beehaw now), but I'm getting shown posts very near the top of the list from, like, 20-30 days ago, sometimes even going as far as a year or two ago. They haven't that many upvotes or comments either. Anyone seeing that?
I'm sorting by Hot. I've came across this thread on AskLemmy about the same problem, and one of the comments seems to allude to what you're saying, adding that a server restart seems to fix the problem temporarily.
Unfortunately, while people are continuing to join and exodus reddit. I'm reluctant to make a server change even though it would only be down for a minute or so. I'll probably schedule it for later today or tomorrow once the initial wave of people have all joined.
To give you an idea, we were processing around ~30k requests per hour. That includes federation traffic. We are now processing ~90k requests per hour!