People joing and crashing server

Hello could do with some help, when 90% of people join my server everything works fine but every now and then someone will join and then the whole server crashes its a fresh install (server side) and i have no problems running it. I also get no errors when this happens either? Do i need some type of protection?

Got some more info? Because the developers can’t solve an issue, if the issue itself isn’t that clear to begin with.