That ain't a bug. You've hidden every post in-between pages.

This is Lemmy's way of telling you to take a break lol. In all seriousness, there probably is a finite end to posts sorted by "Top X" when you look at the entirety of posts that fit that criteria. Idk how the different sorts are scored but the theoretical max of all posts would only be those that had interactions and upvotes in that period.

I'm just speculating so don't take this as the truth.

The only way to fix this is to post more content in that 6 hour period.

Maybe you just finished the whole feed hahaha

What happens if you try other sortings?

Just disable page dividers.

You could try turning off Settings shortcut: Post options > Display page dividers