internet speed is slow on nighthawk r7850 when wired

[rred202020]

When i  hard wired the router to my computer  my internet speed is about 200-250 mbps. My (Spectrum) provider is at 400 mbps. When i plug straight into my moderm i am getting 400-450 mbps.  I also found out that when i check the Qos box on the Nighthawk router, then uncheck it, the speed would then restore back to 400 mbps. but after a day it go back down to 200-250mbps. I have also update to latest firmware V1.0.5.64_10.1.74 . This is really annoying when you are not getting full speed through the wired. There is somewrong with  firmware that developer need to look at. If anyone got any idea, please let me know. I have also  try reset and update.

[tooltime63]

This is actually for the Nighthawk X6 AC3000 R7850 but is not included in the mandatory list I had to select to post this reply (smh...). I have the same exact problem. I have 450Mbs down from provider but more often than not, wired ethernet testing gives less than 200Mbs. If I connect directly to Spectrum modem, I get the 450 speed again. If I do a hard reset on the router, I get the 450 download speed again for a couple of days but then back to the slow 200 or less and the process repeats. I've tried changing a few settings but nothing works. I thought I did thorough research when selecting this modem but am now quite unhappy with my decision. My firmware for the R7850 is V1.0.5.68_10.1.75.

[rred202020]

So i bought another Router, Asus RT-AX82U.  I am getting full speed with this new router, so there is something wrong with this NightHawk router software here.  Sometime the Wifi would drop down to 1-2 mb then i have to restart router or change the channel.  They need to fix the  software for this  replace us a new one, i just bought it over a year. This is 200 dollars router.