@TP-Link 

Hey, thanks for the repsonse. I'm not sure I got your mail. 

Sorry for the late reply, I had been testing different things and trying to see what might be causing the issue.

1)Yes, All the 2.4ghz devices do have this slow speed. 

2) I have around 15-20 devices on the 5ghz network, only around 6 or so using the 2.4ghz network. The 5ghz devices vary, the 2.4ghz is a chromecast, older laptops and older android devices. 

3) I was able to check the link speed on my Laptop, it showed as 300mbps. On my phone, it fluctuated from as low as 15mbps to as high as 144mbps. This is while I connected it to the guest network which I set up to only broadcast a 2.4ghz signal, as these devices would otherwise connect to the 5ghz network and I'd have no way to test on them.

I have 3 Deco S4's. I have my main Deco plugged into my router which is in modem mode. My Main deco has a TP Link ethernet switch connected to it, and all ethernet ports on the switch are in use, though all the devices aren't always on.

While I'm not certain, what I seem to have found is that only the main deco has the really slow 2.4ghz speed. The 2.4ghz network on my upstairs and downstairs nodes works OK.  My ethernet speeds may also be slower than they were before, though I'm not 100% on this. 

The speed seems to fluctuate at complete random. Currently I only have 2 devices connected to the 2.4ghz network. A few minutes ago, I was getting great speeds of over 70mbps, then a few minutes later it dropped down to around 1mbps (yes 1), and then it can hover around 10mbps. 

@TP-Link I appreciate the repsonse but I don't think what you are saying is accurate. 

My old Virgin Media Superhub 3 never had this problem, and I only changed around a month ago. I don't see how it can be a problem with interference when my old hub worked fine. 

I have even tried it when most devices in the room were switched off. In fact, I went to the room my main Deco was in and placed my phone right next to the Deco and got the slow speeds. That can't be due interference. 

In addition, my other nodes work fine on the 2.4ghz network, it's just my main one that is having issues. 

@TP-Link To further update, the performance just seems all around spotty. Directly after a reboot, the speeds will be fine on 2.4ghz, but some time after, it will drop off again. I do not understand why this happens, and I really don't think interference can be blamed. 

In addition, I have noticed that the 5ghz network is also having issues. There's an area of the room where speeds will drop down and fluctuate, yet take 2 steps towards the center of the room, and speeds will jump up to what they should be. To clarify, this room is directly below the room with the router. 

This, again, does not seem like interference, and I would appreciate any tips or troubleshooting steps. Please don't ignore me on this forum. 

@TP-Link Hello, I have done all of these. I tried everything I could. Changed the main unit, reset the Decos. No matter what, the 2.4ghz network is spotty. I set up my old router again, and that has much more consistent 2.4ghz speeds. 

How do you explain this? What can you do? I don't think the S4's should be performing like this. It's always the main Deco that has the issues, the other ones seem OK. My old router that I set back up is in the exact same place my Deco was with the same setup.

It seems that if I reboot the network, it will work OK for a day or so. Then it goes back to being slow. I'm not 100% on this last part though. What would you do in a situation like this? What can you do to help fix this? I find it odd the S4's would have this flaw.