Wired network issues but wifi works fine. On two different routers on three separate computers

[Azela]

Hi all, 

 

So I'm here with a bit of a problem. Recently our internet speeds have been cutting in and out on our wired ethernet connections. I say our because it's happening to every computer plugged into the modem/router. Had a cable technician come replace the router and verify signal speeds to make sure it wasnt the router or my ethernet port / cable on the computer sides. Since this is happening to every computer on the network but our wifi speeds are not impacted I wanted to see if anyone had some troubleshooting steps to recommend because I'm at a loss. 

Let me know if more info/clarification is needed. 

 

Thanks in advance for any help.