C6300BD periodic disconnection issue

When I renew 2 year contract with Cox Cable company they replaced our modem, which is Netgear C6300BD, about 2 months ago. 

It's been disconnecting periodically, about one time per 1~2 hours period, which causes stopping YouTube streaming, Internet radio, downloading, kicks my boy out of his Xbox team play, etc. It backs up after very short period of time. When it disconnects both wired and wifi disconnect at the same time so I assume it's not isolated issue. Someone suggested to downgrade the firmware version to solve the problem but it looks like it's a new modem and it doesn't have other firmware versions.

Our family had no problem with previous modem for 2 years but new one has this problem. So I assume it's the modem. I've searched Internet hoping to get answers but I'm ending up posting this question. If anyone has any clue about the problem and share then it would be much appreciated.