This is less of a bug and more of an exploit. There is a thing called AFK fishing. AFK fishing lets players obtain powerful loot effortlessly and without even playing the game. Some of the loot may contain stuff as powerful as mending books! AFK fishing works by having something hold down the right-click button on a mouse while holding a fishing rod in an AFK fishing machine. AFK fishing machines have a right-clickable block such as a note block so that players can infinitely use the fishing rod while AFK. Some players even install auto-clickers to AFK-fish. This exploit ruins the game because the game becomes less about skill and more about who can leave their computer on the longest. This puts players who play the game legitimately at a disadvantage.