Router Dropping Internet Connection

I have a Netgear AC1600 R6250 Smart Wifi Router connected to my iMac, MacBook Pro and MacPro from a satellite modem. The router constantly drops the internet connection after a few minutes. When I then re-plug the ethernet cable from the modem directly to my iMac, the internet is immediately re-connected, so the problem is definitely with the router. A friend suggested it could have something to do with timing out or an IP address conflict. I do get this message when I first turn on the router: “Another device on the network is using your computer’s IP address XXX.XXX.X.X). Try connecting again later. I f you continue to have problems, change the IP address of this computer or the IP address of the other device.” After being able to connect, when the connection is dropped, I get these browser warnings: “Secure Connection Failed. The connection to www.XXXXXX.org was interrupted while the page was loading. The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.” OR “The connection was reset. The connection to the server was reset while the page was loading.” Again, when I plug the ethernet cord directly from my modem into my iMac, I get immediately connected to the internet. Is there a setting in the settings configuration that will fix this problem? Many thanks! Robbie Leppzer