TP-LINK should be ashamed of the fact that it treats its users this way! People spent a lot of money buying their products and they must be sure of the technical support of these products! It is unfortunate that they do not even bother to respond to their comments and the company is in no hurry to fix errors in the software, which it fixes for an impermissibly long time! And no apologies to users! From myself I can only say one thing - I am very disappointed! Most likely this is the last product that I purchased from this company. I wanted to buy a Mash System for home, but I'm afraid I will choose another company. Sorry, I just could not stand this attitude ...

Apparently it's time to sell this device and choose a new one and definitely not TP-LINK company. I will never purchase your company products again! I can’t understand one thing - why is this attitude towards users? Is it really difficult to keep them up to date so that they do not feel simply deceived? Information zero - released beta and all. Without even removing the problematic firmware from the sites. Are they working on corrections or not, when is it due to wait? So far, only some questions to company representatives, but no answers! Nowadays, this is not done and is not done to people who support the company with their money, buying obviously raw products!

@Kevin_Z Is there any new information when a new firmware for the device appears (not a beta version)? Release the beta version as the main firmware, since it is not convenient to use the web interface on beta (everything is in beta inscriptions). I personally have no complaints about the fixed beta version. I will be grateful for the answer!

@Sergey_Miklukho 

Have you guys even tried disabling SPI FIREWALL in settings??

Spi (Stateful Packet Inspection) will most likely be the culprit for bad/slow Internet Speed as well as ANY incorrect QOS settings..

SPI is a feature which halts data traffic aka data packets and inspects/scans them before letting it pass through the router and to the host ..

Also, if you could post your configurations here I can tell you more accurately if something has been set or configured wrong. 

I have this router for a few years now, and I've never had any issues with it.. I run 12 wireless devices off this router including 2 wireless IP CAMERAS, stream 4k on 3 devices at a time wirelessly, play games etc.. 

So IF YOU are getting 900Mbps-1Gbps to your modem, but half that speed on your devices.. Then 200% you've either not configured your router correctly, or you're not using a cat6, cat6e (either  one is fine) ethernet cable..

Make sure IPTV is not enabled otherwise NAT and NAT BOOST will be disabled..

Advanced>>Firewall>>uncheck SPI FIREWALL.. And if you don't have a landline,sip,voip phone.. Uncheck SIP ALG as well .

Good luck. Let me know how it goes.

***Note**** once you've made the above mentioned changes, save all your settings accordingly and reboot the router just to "refresh" all loaded parameters and protocols from its memory cache.

Good luck.

Apparently, the company stopped supporting this model and left its customers to deal with the problems themselves. This explains the fact that the company's representatives stopped in any way to react to customer reports about problems that have arisen, which are clearly of a technical nature on the part of the manufacturer. This is my last device from your company! I spent a lot of money on the purchase of your product, and you act so ugly with your customers, leaving them and do not even deign to reply to messages! Shame on the company!

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...