The thing you just stated is called a "Glitch" It's more prone to happen in twinswords for some reason but it also happens in other mods too. In aikido, If your tori does a random move instantly in the first frame, its a glitch. In twinswords when a part of player touches the ground outside the ring, nothing happens, its a glitch. Tho i have noticed that certain parts tend to glitch more than the other ones.