Personal router is not working with any modem - SB6141, SB6190 with NetGear AC1900, Linksys EA 7500

[hp25]

My personal router can not keep up the connection with my modem. I had ARRIS SB6141 with Netgear AC1900 router. Suddenly I keep loosing my connection ( I have 300MBS connection). I have changed router to Linksys EA7500 and same issue. I change my  modem to SB6190 and it still the same issue. If I bypass my router and connect to modem directly, connection stays on. But I need more ethernet port and WiFi. 

I finally have to call Comcast tech and user their rental modem XB6-A. I don't wanted to pay monthly rental charge. 

Anyway,  to find out what could have been the issue with my modems and routers. 

[CCAndrew]

Contact any of the modem or router’s manufacturers. You already proved it wasn’t a Comcast issue when you plugged directly into a modem. That’s where their responsibility ends if you don’t use their equipment. In any of the scenarios you tried, did you ever change the Ethernet cord between the two?

[hp25]

Thanks for the input. 

Both routers are brand new and SB6190 is new. Do you think there might be some issue ? 

[CCAndrew]

Sure there’s an issue but neither brand is Comcast and you stated the internet is fine out of the modem. It isn’t Comcast’s responsibility to ensure 2 devices that isn’t theirs functions properly. Its either the manufacturer or user error