@SoCalPhilZ thanks for that. Let us know how you went with their finding. Hopefully there is a fix.

@kooldavid I do that too (rebooting @ 3AM automatically) but does not seem to help. 

Tried all suggestions here and on the web but nothing seems to work. 

Will replace this router w/ my old nighthawk and if that solves the problem I am pursuing a warranty claim on my less than 1 year old TP-link router.

Not happy with the customer service so far. No phone access, no email access and the fact that their automated form for complaints does not accept this model router (even though it is listed in their drop down menu!) does not give me any confidence that they can fix anything.

Lesson learned.

No more TP-link products any time soon.

The latest update.

I opened a tech support case yesterday (Saturday)  and shared with tech support that this problem is becoming more frequent via a chat session.

In short,  my router is 7 months old,  the router has a 2 year warranty, I provided proof of purchase....etc

TP-Link tech support emailed me back with some steps to get the router replaced in less than 24 hrs.

I will share updates as I porgess through this process.

At this point,  in less than 24 hrs  tp-link has provided a solution.   

I am actaully impressed that not only is tp-link tech support avaiable on a Saturday but they got back to me in less than 24 hrs on a Sunday with a solution.

BTW, I am curious,  for  those of you that have this random reboot issue, "What is the HW version of  your router?"  Don't rely on the GUI,  look at the actual label on the bottom of the router.

I have v2.8  yet the GUI showed v2.0.  FYI..The latest HW version is 3.x. 

@SoCalPhilZ 

Latest and maybe my last update.

- TP-Link Support - I am impressed with thier tech and customer support.  Honestly, one of the best I have ever dealt with throughout this process.

- I did a standard advance replacement and  even with Covid-19  delays in shipping the NEW and not a white boxed refurbished  unit showed up in 10 days.

- You can pay for a  2 day advance replacement  for 25.99. 

- TP-Link gives you 25 days to send the old router back.

- YES you have to give them a credit card if you choose the advance replacemnt method.

- The cheapest replacement method is to send them the old router back first. 

For those of you that have a HW problem.  I  hope this helps.

- TP-Link routers come with a 2 yr warranty with no BS in fine print of what is NOT covered. In short, they stand behind their product 100%.

-  Keep your proof of purchase (I bought mine from Bestbuy using Google purchases, so  it was easy to track down if you lost the orginal POP)

- Regiser your  router with TP-Link.

- Have access to or take a picture of the  serial number located on the bottom label of the router. (That is where your HW version is too)

- Do a live tech support chat and go through the same troubleshooting you just did before contacting them :-).  ( Even though you are an IT engineer with 20 years of expirence, be nice, they are there to help, not be  abused becasue your frustrated)

- BACKUP your  router configuration. This make replacing your router a 15 minute plug and play event. 

Thast's all I have to share and hope this helps. 

@SoCalPhilZ 

SoCal, Wish I can follow you and say that TP-Link stand by their product. Mine is the AD7200 and it was having this disconnection issues. After all the updates and additional updates and troubleshooting They pretty much gave up and only option I had left was to keep rebooting the router. On one of those reboots "power off and then power on) the rounter smokked. I insisted on getting a replacement and after days of push backs they agreed to replace it.

When the replacement arrived it was a different router with a different serial number. But when i powered it up it had all the configuration that was in the replace router that I could not reset because it fried, including passwords!!!! How could that be? Did they just replace the power module and transfered the internal componebts to another empty box? Could TP-Link think that small when it comes back to their customers?

Less than one hour after connecting it my wife got disconnected from an online project meeting she was heading!. So I'm back to troubleshooting. Went through the first chat session, got scheduled for a call back that came. But 2 hours later the tech that called has not sent the email he was supposed to send to me on what to do. So I went for the second chat and now waiting for another call back!! Definitely not my idea of a vendor that cares about its customers

I've been having the same issue with internet disconnecting on a number of routers as well. But I found out that you can go to the router dashboard select Advanced>Network>Internet> Click on "Release" and after Click on "Renew" to refresh your Dynamic IP and DNS addresses. I too used a USB CPU fan resting on top of the router to keep the router cool and it did reduce the number of renewals i need to do but does not eliminate to problem.

Hope this helps.

@ram1220 I have the same problem. After update to the latest firmware, the network becomes unstable either the signal drops or the network disappears. I tried to do a factory reset and set up all again but I still have the same symptoms.

@KatsumiJunior 

Update 05/2021 - The C4000  v2.0 replacement router I received  08/2020 started the random rebooting again. I contacted tech support with all of the same information as before and they  promptly  issued a RMA and new router was sent to me.   It cold be a coincidence,  it seems they  both  started having this problem after 7 months. 

The new C4000 router is a v3 model and has the latest firmware.  Now the frustration.

- The C4000 v2.0 backup can not be restored to the C4000 v3. I had to setup the router in such a way that I could look at my older v2 router and go  through page by page to duplicate  the settings in the new v3 router.

- My 2 TB USB drive used for my Time Machine backup is not being recognized by the new v3 router.  If I need to restore anything I  will have to  plug the HD directly into a computer.  

- My new USB drive is recognized and shared for use as a Time Machine backup but none of my MAC computers recognize it.

I think these  units have a  design flaw and although  tp-link stands behind the product if you can show proof of purchase, I would not recommend this product to anybody.

I will not buy anything again with the tp-link name on it.