Irregular Intermittent LAN, Wifi, and Internet outages

I have a strange issue with my Netgear D6300 Wifi-ADSL Router.
(All I want to know is if this is a Hardware Issue and I need to get a New one (or) if this is a Software Issue that can be Fixed?)
The Firmware Version on my Router is the Latest V1.0.0.102_1.0.102
And then it would be great to know how it can be fixed.
The Router is never used on ADSL, but as a Plain Wifi Router, with Broadband Input on PPOE with a Static IP, and no Password.
The Phones, etc, connect on Wifi, while the PC is on the LAN.

I had been having a lot of Interruptions in my Internet Connection. And I always thought that the fault was with the ISP. And they too came more than once, to boost the Power of the Fiber Optic line, etc. But the fault would again keep repeating.

One of their Tech Support guys, suggested me to run two Pings simultaneously with a -t switch. So that the Ping would keep going on - One Ping to their Gateway IP, or any IP or Domain online. And the other to the Router IP.

I did that.

I found that every time the Net disconnected, both these Pings would also get disconnected - simultaneously.

The Tech Support guy said that thus it establishes that the Problem is with your Router.
Because it is your Router that is terminating the Connection, and not us.

So, this is what the Ping Messages come during the time of Disconnection.
General Failure (a series of that)
Request timed out (a series of that)
Connection restored for just one ping.
PING: transmit failed. General failure
Connection restored for 7 Pings
Request timed out.
Connection restored for 2 Pings
General failure (a series of that)
Request timed out (a series of that)
Connection restored for 1 Ping
PING: transmit failed. General failure.
Connection restored for 7 Pings
Request timed out (a series of that).

Strange that when this happens, the directly connected PC on LAN cannot Ping. And the Mobile Phones connected on Wifi also lose the link. So, it's not just the Net Connection, but the LAN and the Wifi Link that all have the outage at the same time.

So, whatever is happening, it is isolating the Router on all 3 connections.
Whenever it is restored, it gets restored on all.

Now the Intermittent Connection Problem is NOT UNIFORM every day. Some days the whole days, I probably would have observed disconnections only about 10 times. And some other days, it is nearly continuously disconnecting. Disconnecting 10 times or more in an hour.

I of course tried Factory Reset.
Seemed to instantly give an improvement in the frequency of the Number of Disconnections. But still had atleast 10 Disconnections in a day. Which again progressively worsened.

I was already on the Latest Firmware. But I thought I would update the same again.

First time, I tried. I had the same Disconnection Issue happening even while I was updating.
The Second time, it went through to completion.

I set up the Wifi and the Net Connections.
But the Disconnections still keep happening. Atleast 10 times a Day.

Am wondering if I have to change some Software Settings. Or maybe this is a Hardware Issue.

Would be so Grateful if you could help me on this.
Thanks much.
Shrikant.

P.S. I have attached a Screenshot of the Ping Window, at the time of the Outage, to show how it looks like.