Internet Connectivity & Wireless Network Problems with New Modem/Router

I have a new NetGear C6300 [https://www.cox.com/residential/support/netgear-c6300.html ] and am experiencing a couple issues and wondering if anyone has insight:

I am working from home with a company router and VOIP phone (ethernet), in addition to a personal laptop and phone (wireless). The company network typically falls off once every 1-2 days and whenever that happens they advise for us to restart everything to get back online.

After one particular outage the connection wasn't restoring after three restarts, but all lights on my old C6300 modem were green and on, so I called my ISP (Cox). They said their signal was intact and advised my personal modem/router was faulty. I purchased a new replacement C6300 and the same issue persisted. All lights were green on the router and the tech provisioned my new equipment but neither ethernet or wireless worked. I asked her if we should turn-off and turn-on everything and she said it wouldn't make a difference, but after hanging up the phone I did just that and everything was working fine.

The next morning during the 7am hour my internet connection drops for five minutes and restores itself. Later that night during the 7pm hour the connection drops again for and is restored in 6-7 minutes, This persists over three weeks with the 12-hour rolling dropout time moving into the 8, 9, 10, 11 o'clock hours.

I call ISP Cox and they say everything looks good on their end and re-provision. When the system comes back, the 2G wireless doesn't work and they schedule a Cox tech to come out. The tech doesn't find anything wrong with the signal and factory resets the modem. Now I can see the wireless networks and the Nighthawk app and the devices show connected, but no wireless internet connectivity.

I called NetGear which said that the ISP needs to lock uplink and downlink channels. I called the ISP and they said they don't do that.

Summary:

1 - Both wireless networks show, but I can only stay connected to 5G. I can log onto 2G, but get kicked off and it states the password is incorrect. I know the password is correct, and it allows me to logon again by using it.

2 - The rolling 12-hour internet disruption that tales out both ethernet and wireless persists.

Observations:

-The internet time is correct on the modem.

-Several DDOS and DOS attacks are on the log

-Disable Port Scan and DOS Protection is not checked DOS and enabled

-Nighthawk app says my firmware isn't updated, but the version reads as most recent V1.03.04. One of the techs said that sometimes firmware updates result in the unit not working, so I am hesitant to update to the latest version.

Not certain what to do next.