So my understanding of "the issue" is that it's not quite the sorting algorithm that's broken. Instead, it's the process that calculates and assigns scores to posts. This process runs separately or independently from any user viewing their feed. It seems, from what I've seen, that it runs in the background. And so the issue is that this process can get behind and fail to update all posts, leaving some with scores that are too high because their age isn't reflected in their score. It also seems that it is older posts that are left un-updated.

So the result is older posts appearing as though they're more "hot" than they really are, sometimes really old posts that are not "hot" at all.

From what I've seen this has been fixed by substantially speeding up the process that calculates scores and we could see it in the next version.

The upside, if I'm right, is that "hot" isn't ever really broken. Instead there are stray posts floating around that look hotter than they are. If you're willing, and these stray posts aren't too numerous, you can just skip them and still read through a "hot" feed. From the few times I've seen a problem, it was really obvious which posts were these "strays" ... usually just way too old compared to everything else.