Server Disconnect issue - hosted server

[bulletbutter]

I have a hosted server (survival Servers) and I currently only play with one other person for testing reasons before server goes "public, public". The issue is that the person who I am playing with often has a network disconnect every 15-20minutes or so. Has anyone come across this issue? Is it because we are on the same network or is the host just not very good? We are both playing on a wired connection. Could it by an ISP issue on my end? I am leaning towards wanting to say it is because we are on the same network and it is causing issues?