I've been using these Deco Mesh devices for almost two years now. Two of them (Green and Blue, as shown in the picture) have had no issues at all. However, I'm having trouble with the mesh located on the 3rd floor (Red Mesh).

What I find strange is that even though the Red Mesh is connected via Ethernet to the Green Mesh, which is my main unit, the speed is significantly slower. I’m not sure if the issue lies with the Wi-Fi signal on the Red Mesh, but I’ve tried everything: swapping the Red and Blue Mesh units, updating the firmware, and even performing a recovery via a computer—but still no luck.

The reason I suspect a Wi-Fi signal issue is that when I connect my desktop to the Red Mesh via Ethernet, the speeds are just as fast as the Green Mesh. However, the wireless speed is far slower.

I can also confirm there is nothing wrong with my Ethernet cable—it has been tested and works perfectly with other devices and setups.

After some research, I was advised to update the firmware of my Deco M4 (Red node) to the latest version—1.6.2 Build 202040308 Rel. 55841 and made it my main node. The network optimization feature appeared, so I ran it. But, when I tested the speed, to my surprise, it was still disappointingly slow. At first, I thought the issue might be with my slave nodes, as I had placed all three nodes on the same floor wirelessly. But even after turning off the other nodes and leaving only the red node on, the speed was still terribly slow. (I got 700kbps speed) 

I’ve been trying to figure this out for months, but I haven’t been able to find the help I need. Any advice would be greatly appreciated!

My Deco setup (Image)

https://imgur.com/a/PsG0VDd