Communities on big servers not showing all (or any) posts

Hey, first off, I really appreciate what you are doing here with this Lemmy instance! This was the first one I joined during the Great Rexxit of 2023.

However, about a week later, I created another account on a larger server (.world) and using that as my main because I could not find a lot of communities on this instance at all (!mlemapp@lemmy.ml was the first one I tried where I had this issue, but the majority I tried to subscribe to at the time were not showing up at all, while lemmy.world could see everything except BeeHaw). With the update to 0.18, this got a lot better, where I can just keep retrying until it finds the community.

Of course, .world got super overloaded at the beginning of July with everybody finally leaving Reddit, so I subscribed to all the communities I had there over here on the Outpost, but over a week later, some communities still are not showing all posts. The most egregious example I have is !antiquememesroadshow@lemmy.world, which still isn't showing any posts at all on this instance.

Now that things have been going better with .world, I've been directly comparing the two and I'm still missing a lot of posts here that I can see on .world (whether the community is on .world or elsewhere).

Is this a Lemmy glitch? Can anything be done about this? Thanks in advance!