Foreign Symbols appear in Chat causing crashes

Every time I try to play on my Minecraft world, these strange foreign symbols suddenly appear through Chat and they cause so much lag that the game freezes, sometimes even causing the game to crash. My friend told me to disable command blocks and it worked, it prevented this bug from occurring. But I would much more appreciate it if you were to find a way to ending it entirely because just 2 days of this madness was already enough for me