So I had made a post regarding sorting posts not working, but I have noticed another issue where some communities just don't have some older posts. I have tried both on web and on android app, and it's the same, tweaked some settings too. A demo video (GIF) showcasing the problem and my account settings are attached in below Imgur link: https://imgur.com/a/8X8AQpI
Bit old, but I noticed something too so hopefully it helps: It appears that selecting either all languages or none cause all posts to be be shown, no matter the language. (and since it sounds a bit ambiguous, no, it won't show hidden or blocked stuff)