game ends when someone joins

i put gamemaker server in my project, it was a bit broken so i went in the data.win with undertale mod tool to go fix up some stuff with it
basically, login and connecting works.
i was testing the online by opening the exe twice and then logging in with different accounts
basically. so:
i join the game, then my alt joins the game. the window with my main account freezes, then it ends after a bit. then my alt closes too

yea, thats it. please tell me how to fix it!