@Kevin_Z  Hi, I am C5400X user and I have the same issue, just found this forum, could you send me the beta firmware to test it out? Thanks.

@Kevin_Z Could you please send me the firmware beta too? I'm still having lots of issues.

@Kevin_Z Could you please send me the firmware beta too? I have the speed issue. Thanks

I also own a TP-Link C5400X V1 which cost me a lot and only recently discovered this discussion on the gigabit speed issue that I'm also experiencing, having just switched to Gigabit internet plan recently.

I've updated to the latest firmware and was able to get up to 750Mbps. Previously, I was able to get full-speed at 930Mbps which then dropped to 300Mbps after some time and I kept wondering whether it was my cabling in-house, but as it turns out it's thanks to this expensive door-stop from TP-Link.

Please TP-Link update your firmware regularly, especially for such a glaring bug such as this. The latest firmware is now several months old (5 months old since Jan 2020) and there are no further updates.

NOTE: It seems that the following steps will resolve the Gigabit bug issue:

1. Qos: Set your internet speed MANUALLY eg. 1000Mbps/50Mbps (this is as detailed already above by another poster - RepostPolice)

2. DO NOT SWITCH ON ANY APPLICATION OR DEVICE PRIORITY QOS. I discovered that switching on Device Qos even if prioritising your device it will throttle the bandwidth to 750Mbps - no idea why you'd think "high-priority" means MAXIMUM available bandwidth!

I've noticed a similar issue after upgrading to gigabit internet.  I'll get full speed for a day or two if I try to use QOS and then it drops to about 450 Mbps.  Rebooting gives me another 2 days at full speed.  If I turn off application priority and make sure no devices are selected either, it stays at the full gigabit speed without slowing down.  Done everything else I can including downloading the 1.1.2 that is currently available, reloading it, resetting and setting up again, etc.  It looks like this unit simply cannot handle QOS for more than a couple days without dropping speed.  So now I have to run it without QOS and just deal with the fact that when someone uploads a YouTube video, our ping jumps through the roof because they eat the entire 35 Mbps upload limit.  I really need to use QOS but can't and still run the internet at full download speed.

And I agree: we need more proactive updates.  It's a good piece of hardware but the software is lacking!

Mike

can you send me the beta firmware (2018) i have the same issue :(

@Taserface The current/official version is later than the beta and it still doesn't fix it.  I need to run QOS for bufferbloat so I set it up to reboot every morning at 5am.  It is working well like that but I wish tp-link would fix it so I don't have to do that.

@Kainthes Never had a problem yet, love the router. got the beta version running. and can say its been running for over 3 months no problems