This bug is incredibly annoying, as the only way to fix it is to restart Minecraft. This bug first appeared after the 1.16 update. Whenever a pause menu opens, a loading animation appears, and never goes away. I can still move around, but I can't mine or place anything. I tried waiting for hours to see if it would go away, and it didn't. I disabled all my texture packs to see if that would do anything, it didn't. If you want to see the bug, I made a video about it.