@MicroThin 

Same Issue here, I contacted Chat support and went through all the steps, resetting to factory default many times, changing channel and channel width on both 5G1 and 5G2, did nothing.

It's still until this moment happening, both 5G1 and 5G2 randomly disconnects and the only way to bring it back is by physically rebooting the router. 2.4 is fine.

After spending so much time with the chat support, they redirected me to a website with a number to call a rep to order replacement, I submitted an email today, hopefully will hear from them soon.

I have the Archer C4000.

@MicroThin 

Attempt the below, one at a time, to see which yields better result:

• Feel the router, if the router is hot or lots of heat coming out, use a fan to cool the router, a regular fan or USB fan is fine.
• Set the WiFi Transmit Power to low (if the setting is currently set to high), and see if this helps with the WiFi issue. When WiFi Transmit Power set to high, the router consumes more power, creates more heat, might cause instability.
• Review the Wireless setting, under 2.4GHz, adjust the Mode, b/g/n or b/g or n only (don't forget to click SAVE).
• Next, perform similarly with the 5GHz setting if the above did not help (change the 2.4GHz back to previous setting).
• Disable the auto channel for 2.4GHz, use manual, then perform similar for the 5GHz.
• Another option is to separate the 2.4GHz and 5GHz WiFi SSID along with different password to see if this helps. For example, SSID tplink1 - 2.4GHz and SSID tplink2 - 5GHz, different password for each.

Possibly lots of trial and error to troubleshoot. Additionally, review the firmware and see if it is the latest, might help with some of the issues.

@Godzilla 

I have tried all this with the support on chat, none helped.

no heat.

@MicroThin I have setup 2 more C4000 recently all working fine. Change the the WIFI security version and encryption from AUTO on both and see how that goes. 

I bought a C4000 v3.6 from Costco and it had worked great for about two weeks. It came with the latest firmware installed. Last night the second 5G radio started going haywire. This was the same reason I stopped using my Netgear R7000 which had previously worked fine at my old house (for years!) and suddenly started having 5GHz issues at the new house even with almost no neighboring wifi interference. I have the C4000 set up as an AP only with separate SSIDs/passwords for the 2.4GHz and each 5GHz radio. I only care about speed on the second 5GHz radio and use the other two radios for IOT stuff in my house. The fix for 5GHz-2 was manually specifying all settings, with channel and channel width being the key I believe. Specifically, I had to bump the channel width down to 40MHz on the 5GHz-2 radio. The first 5GHz radio is set to 20MHz width which can provide up to 160Mbs per device which is plenty for streaming boxes and whatnot. I had been getting 650-800Mbs real sustained transfer rates with an 80MHz channel width on 5GHz-2 but now get only 320Mbs max at 40MHz width.

@Qwerty44 

I installed a new C4000 (US) Ver 3.0 yesterday (replacing an ASUS dark knight)

I purchsed it from a well known Canadian computer store 

- The latest firmware was already installed, so I assume I got a recent build unit

- WiFi worked well for the first couple of hours on all the 3 channels

- I enabled "smart connect" 

- I could not reach my Brother printer via WiFi

- I disabled "smart connect"

That's when all the dropped connections starting happening

> Randomly 3 each of the WiFi bands were "unreachable" from different computers or my iPhone

- I reset to factory default and did the installation & setup again

- Same problem as before, I can't get a connnection anymore to any of the WiFi channels

I initiatied a return 

@MicroThin 

I think the main problem here is the latest firmware, I contacted support and asked for a replacement and did get the replacement.

I noticed there was a firmware update, but since I read somwhere that it could be the firmware, I decided not to do it. it's been working fine so far...

MicroThin wrote

New install only couple weeks old and end user is finding 5G just stops working. The router is up and working as I can connect remotely without issue

 

I had end user connect to 2.4G without issue. Only way to fix connection to 5G issue is to reboot router

 

TP-Link - There is something very wrong with the Acrcher range and 5G. I have the Archer AX6000 at home and it has also done the same thing day one

 

All devices have the latest firmware

 

I have set all WIFI to auto and disabled WPS and other fancy features. Just trying to keep it simple