Hi All I'm running a headless factorio server on a physical linux box for myself and a couple of friends. It was working perfectly up until Saturday night/Sunday morning, when it got really laggy for my friends. If I connect to the server using the local LAN IP address, it is fine, map download spee...

Did you get this sorted? Having the same issue here. Mine is a second instance on a server already running on instance fine. I suspect it's a config or server settings thing, but not sure what exactly.