The game glitch instantly after connect to server

I build a dedicated server by myself and everything was all right. After the first day, one of my friends can't connect to my dedicated server, every time he tries to connect will crush his game instantly. He tried reboot computer, reinstall the game, close all the mods, none of these works. Other people connecting my server with his account will cause same thing happens. He is still able to play on other servers but only glitch when connect to mine. On the third day, same thing happens on my account as well. I have check the log and couldn't find any problem in it. Maybe rebuild a new server will fix the problem temporarily but I am worrying same problem happens again.