I recently purchased the C5400X and appear to have the same issue as others in this thread -- where my internet speed drops over several days and a router reboot is required to bring it back to full speed. I have gigabit internet, and after a router reboot, I get greater than 900 Mbps on my LAN PCs. After a week, I get less than 400 Mbps. I was running the latest published firmware. Today, I updated to the beta firmware (posted in this thread). The beta firmware is six months old. Why hasn't this firmware been officially released? The "TP-LINK BETA" pasted over every config screen is quite annoying. I plan to return this router before the month is up, which is quite disappointing.

@Carl, thanks for the response. I look forward to an update from your engineering team.

The updated firmware appears to have been posted (January 14, 2020 release).

https://www.tp-link.com/us/support/download/archer-c5400x/#Firmware

I updated my TP-Link with this firmware and I am having a new problem.

Our internet provider has replaced the cable modem 5 times now. For whatever reason the tp-link will every once in a while the status light turns orange, at this point there is no internet access. It takes about 5 minutes before the status light turns green, and then were back on-line again.

I have tried everything except getting an RMA for this router. The log file has nothing in it at all.

Anyone else seeing this problem?

@Chaz I have not experienced any issues since updating to the new firmware. My internet performance has been good, and the router has been stable.

Chaz wrote

I updated my TP-Link with this firmware and I am having a new problem.

Our internet provider has replaced the cable modem 5 times now. For whatever reason the tp-link will every once in a while the status light turns orange, at this point there is no internet access. It takes about 5 minutes before the status light turns green, and then were back on-line again.

 

I have tried everything except getting an RMA for this router. The log file has nothing in it at all.

 

Anyone else seeing this problem?

 

Can somebody who updated their router with the new firmware can tell if the problem is resolved ?  If the speed is now constant and not dropping after a while ?  Thanks !

@RichH Just wanted to post an update to my issue, which I resolved earlier today, apparently when you want to upgrade your routers firmware, do not use the web interface to update it, instead download the file, extract it, and then update your router with that, I haven't had a problem since I did this.

I have the C5400 v2 with the latest stable firmware, 1.2.5 Build 20190411 rel.52981(5553).  I had to go into the QoS section of the Advanced tab on the home page of the router setting menu to manually edit the Total Bandwidth entry to 900 Mbps down and 20 Mbps up for my supposedly 600mbps Xfinity service.  At the wall of the house it was around 880 and at the modem it was around 680 or so.  Now, I get anywhere from 620 to 690.  No beta firmware required. 

There is a button on the Basic tab of the Network Map page named Speed Test.  When I tested, it would register no more than 315/12 and that is what showed up automatically in the Total Bandwith entry in both the QoS  Application Priority page and Device Priority page.  When I manually edited the QoS Application Priority page entry to 900/20, the bandwidth restriction to both my wired and wireless devices went away.  It also automatically changed the entry in the QoS Device Priority page to match so that I didn't have to make duplicate entries. 

Hope this helps...