Is your computer in the High Priority list? Does this issue happen on all your devices? How about the device connected wired to the modem?
You may reset the modem and reconfigure it to have a try.
A firmware update is recommended if the firmware is not the latest one.
If my suggestion can't help， you'd better contact TP-Link support for further analyze.

uutommi wrote

Is your computer in the High Priority list? Does this issue happen on all your devices? How about the device connected wired to the modem?
You may reset the modem and reconfigure it to have a try.
A firmware update is recommended if the firmware is not the latest one.
If my suggestion can't help， you'd better contact TP-Link support for further analyze.

Yes, I've updated to the latest firmware, the issue happens on both wired and wireless devices, and my computer is listed under High Priority.

Hmm, that's weird. I haven't meet the same issue. You can contact support@tp-link.com for help.

I'm having exactly the same problem.. bandwidth down to 35-38 MBps with QoS enabled,
with other Modem/Router combos (VDSL2 conection here 50MbitDown/10MbitUp, syncs up great with the Archer VR600)
no such issue.. but other issues with the non-TP-Link devices which is the reason I'm using the Archer.

Has there ever been a solution to this problem?

Thanks!

I've got exactly (right down to the exact remaining bandwidth) the same problem... latest firmware. Any ideas yet?

Same problem here, have 55Mbps downlink, able to achieve 6,1MB download. When I enable QoS, download speed goes down to 3-4 MB/s regardless of settings I use. Tried to fill in correct values (55 Mbps down) and assigned my PC to high priority group. Tried even to fill in fake values 100 Mbps, still no change and speed circles around 3-4MB/s. Tried to adjust high/mid/low ratios to check if speed changes accordingly (set 85/10/5 or 50/30/20), no change - download speed is always around 3-4MB/s. There is definitely something wrong with QoS implementation and unfortunately without this working correctly cant enable limited guest access mode as on my older Archer C5 where I could type in directly maximum speed for guests. Also I set by mistake values in Kbps instead of Mbps and found out that it is probably limiting even LAN connection, because I couldnt even download admin pages how slow it was, even ping went up to 500-1000ms...

Make sure the device doing speedtest is with the highest priority and disconnect all other devices, stop other applications when testing the speed.
Try at least 3 times in different at different times.
If the speed is always slow, contact TP-Link support for help. They may have some solution.

vieldcs wrote

Make sure the device doing speedtest is with the highest priority and disconnect all other devices, stop other applications when testing the speed.
Try at least 3 times in different at different times.
If the speed is always slow, contact TP-Link support for help. They may have some solution.

Well I guess we all have the same problem... it's even perfectly reproducable, you can repeat the same speedtest (and others too) several times, every time
the same result.. QoS on, 38 Mbit/s max., QoS off, full speed.... it's that easy, it's really just ticking the checkbox on and off and "save" to get this behaviour..

I'll contact the support.

Just to keep you in the loop, I contacted support, provided screenshots of bandwith settings and speedtest results ask asked by the first level support.

We'll see. :)

same problem