Friend Worlds not connectable

When me and My friends go to the "Friends" menu to join one another worlds, sometimes the world will not show up; even if that friend is in the world (with LAN settings correctly configured) For example, My friend Joe(fake name) is in a world and wants me to join. He just created it a few hours ago or so and hasn't messed with any of the settings. I go to my friend's menu to join, but it says that he is offline and is not in a world. This is only fixed when I restart Minecraft. I know this isn't an internet thing, because it sometimes happens wherever I am, and it happens to all my friends too.