I'm having exactly the same problem.  I have an Archer C5400 v2 and it seems fine for everything except it's disconnnecting / dropping its connection to Blizzard servers.

I can have 3 computers all connected to Blizzard at the same time and all three will randomly disconnect (but not at the same time). 

It would be good if there was some support looking into this issue.

Same issue here. Even had a replacement and still the same. 

Firmware update needed

@Gwalle any response from TP-LINK support on this issue?

Nope - in the end I'm just setting up as follows:

Modem --> ethernet --> Router (provided by ISP) --> ethernet --> C5400 as access point

This seems to resolve any issues and doesn't appear to hamper speeds... it is annoying I have to use two routers but at least the speeds and 5ghz capabilities are much better than without it.

@Kevin_Z 

Hi mate I've got the same problem with the restarting when playing fortnite

Mine is 5400 v2.1 router

Cheers

@Kevin_Z 

Hey Mate

Its Version 1.2.5 US Version Im in Australia Bought The Unit From MWave

I was connected with live chat yesterday for over 2 hours trying to get help and all they said was return it under warrenty and press reset button

They Created A RMA Request Should I Hold Off On That ?? Im supposed to visit the shop in about 8 Hours 

After I Pressed Reset It Still Restarted Itself While I Was Gaming

Cheers

@Vortex690 

I've seen a few places where this issue has been reported. So I'm posting my solution here, as it's super annoying. 

I first tried sorting this out with tp-link tech support, but that was unsuccessful.

In the end I found what worked and I get no disconnects at all now is to go into QoS setting and change every PC, NAS, Chromecast etc to a high priority device.
The only things I left at defualt were very low bandwidth devices, such as Smart bulbs, smart power boards etc.

Try that, I'm pretty sure this will sort out your issues

Hi Everyone

I am having the exact same issue. 

Model: Archer C5400X(EU) Ver 1.0

Firmware Version: 1.1.2 Build 20191223 rel.73956(4555)  -  Updated via cloud service.

Hardware Version: ArcherC5400X v1.0

I have replaced the original power cord going into the 12V adapter, and changed the power outlet the adapter is plugged into. No matter what variation, the power supply does not seem to be the issue.

I have a lot of devices on this router, many of them are smart home switches and such. 

I use it extensively for everything and it never does this reboot thing until I actually launch Battle.Net and play WoW. Have not tested it with other Blizzard games extensively but the main trigger factor seems to be gaming on Blizzard servers.

I have disabled HomeCare (ie. The firewall, intrusion prevention, and malware protection are off).

There is no option to disable QoS entirely, but I have tried:

1) Turning off Application priority

2) On device priority, I have set all my devices to High. I have also tried only setting my gaming computer to High, or setting all my higher bandwidth devices to High. I have also tried with no devices set to High - no combination makes a difference.

Since this is the latest firmware available, unless there is a version that I cannot find that I should download manually.

Please - this issue seems to have been around for a while now. How can I fix this?

To be 100% clear I have only seen this happening when gaming - no other network use, even intensive, causes the reboot.

I do notice that when it reboots itself like this, the system log seems to get lost or bug out and the only entries I can then see are dated 2019-12-23. I suspect those entries are perhaps from the last time I had upgraded the firmware, but can't be sure. It's weird that normal reboots retain the system log in tact but this seems to wipe it.

Please advise - do I need to go as far as requesting a hardware replacement?

Thank you!