Some community’s posts when viewed from other lemmy instances are not showing up

Here is one example:

• https://imgur.com/o00WaG5 - This image shows a hacker news community when viewed via lemmy.world instance. Here no posts shows up and just a blank page.
  Link: https://lemmy.world/c/hackernews@derp.foo
• https://imgur.com/zDhLf1q - This image shows the same hacker news community when viewed from it its own instance where it was created i.e derp.foo
  Here every posts gets displayed.
  Link: https://derp.foo/c/hackernews

So, why some community posts do show up only in the instance it was created? Or is it a lemmy bug?

This problem also occurs with some other communities.

Apologise for my bad english.