Server cuts out for a few seconds every 5 minutes

So the server works perfectly for about a day, but then after that it cuts out for just long enough to kick everyone who isn’t playing on lan. They can join back immediately, but it happens every 5 minutes or so.

I’ve set up the server at 2 different houses using 2 different modems, currently setting up to test on a third. The server itself shows no problems through the webui, so I’m fairly certain it’s either a problem with the network card in the server, or just the cheap modems isp’s in australia send a out.

Has anyone had this problem? Any tips? Thanks