I am new here and hoping to gain some knowledge and insight for the issue I'm having. It's a long read sorry but I am trying to be as detailed as possible.

I have Comcast cable with 800mb service. I have my own docsis 3.1 MB8600 modem. I have 3 XT8 AX6600 Asus routers. My house is 4300 sq ft with finished basement. I have 1 router on each level but on opposite ends of the house from one another.

The issues I've been having off and on for over a year are poor connection between routers, also terrible wifi speeds, and loss of service.

The 2 nodes are wifi only not ethernet connected. The tri band was off so 2.4g and 5g on separate networks. The nodes would have 31 RSSI and the other around 50 RSSI but show weak connections. I would reboot the system and it would show great for a while then weak again.

Comcast has changed everything and tested lines many times with no issues. This is a brand new home build. But they changed wiring outside the house and inside and tested all the connection points with positive results no issues on their end.

I have about 69-75 devices connected at any given time. Mostly smart switches and cameras. But we do have 8 TVs and 6 smart phones.

We had issues streaming TV service and slow smart phone issues with apps like reddit and Facebook ect. But a huge issue is I work from home and on VPN but the VPN Is fast. I would lose internet connection for my work pc and my IP phone a lot recently. Bare in mind my modem router and switch are in the same room as my work pc. So the work pc and phone are straight ethernet connected off the modem and I'm using CAT8 cable. I had CAT5 before but upgraded to try anthting to stop the issues.

So I finally started to just change settings on the router to try anything. What fixed my issue seems so confusing, and I'm still lost as to why. But I turned off the QoS and also turned on the Tri band, so 2.4 and 5g and the 5g back haul all ran together. Doing this has fixed all my issues but absolutely makes zero sense.

Many times, I've read that the tri band on causes issues. I also had issues with the tri band when I first got this system, so I turned it off and kept the bands separate. Fast forward to now, and it's the only thing that works.

So what the heck is going on?? What or why does it not work with separate bands? I tried to bind or not smart devices to their closest node with no luck.