The players who move at the last second during the countdown in the start are not smart. It is not a good idea to run by youreself in another corner. And you keep doing it.
Maybe those are ppl who are doing it on purpose to spoil fun of others. Therefore whatever you will write or how much you will advise they will not listen to you, cause only thing they want is to make other ppl angry.
Best what you can do is what FL wrote above, cause you can never be sure if those random ppl will not decide to spoil fun again when you will be doing random Lava.