Hi all

Just want to share my experience and insight in resolving an intermittent WiFi speed problem that had been causing me pain for over a year hoping that it can help someone with similar issue.

For over a year now my Deco X60 have displayed intermittent odd issue with WiFi speed dropping from 100 Mbps to approx. 10 Mbps after operating for more than 12 hours. Sometimes it lasted more than 18 hours sometimes it lasted only 6 hours before slowing down. And to make it even more interesting it only impacted my Samsung S20 FE mobile phone whilst my wife Samsung S21 and my son iPhone 14 were not impacted and stay at 100 Mbps.

The problem will not go away even if I reboot my mobile phone and as soon as I switch to different WiFi the mobile speed is back to 100 Mbps. The problem will only go away if I reboot the main unit of the Deco X60.

I originally suspected it was a bug with my Samsung phone and when I upgraded my handset it will disappear therefore I didn't try to investigate it further other than installing a tiny device to restart the main unit every 24 hours.

The issue comes to my attention again when I recently bought a second mobile phone, Hisense Hireader Pro, and it started showing same issue at same time as the Samsung phone. This triggered me to suspect that it is not an issue with my phone but rather with the Deco unit.

My network setup is as follow with the Deco X60 set as Access Point:

Reading through the various posts on the internet related to WiFi speed problem that require daily reboot I started looking for clue from the log file of the main Deco unit by logging into the unit directly via web browser. First thing I noticed was the high memory usage, sitting about high 60 to mid 70% constantly whilst CPU only sit at 10-20%. Once I rebooted the unit the memory comes back down to low 50% before slowly creeping up again throughout the day. I have only about 20 devices that are constantly connected in my home network.

From the log file which is filled with many technical jargons that I don't understand I noticed eth1 of my unit kept turning On and Off, sometimes within milliseconds from each other. This is certainly not a normal behaviour I expect from a LAN port which lead me to suspect that I have a problem with either the network cable or the wall port wiring. And whenever the ethernet backhaul disconnected the main unit switched the backhaul to WiFi backhaul. This occcured hundreds if not thousands of time throughout the day and I think this is what sent my main Deco into a meltdown.

Tue Sep 19 09:14:14 2023 daemon.notice netifd: Network device 'eth1' link is down
Tue Sep 19 09:14:14 2023 daemon.info conn-indicator: <32330300> link event: eth1.down
Tue Sep 19 09:14:16 2023 daemon.notice netifd: Network device 'eth1' link is up
Tue Sep 19 09:14:16 2023 daemon.info conn-indicator: <32330300> link event: eth1.up

After I rewired the wall port socket I noticed the eth1 glitches have reduced significantly but not entirely gone and the WiFi speed issue still persist.

Further investigation along the ethernet backhaul cable from the DECO main unit to the 5 ports Switch that I have in the ceiling I noticed the 5 ports switch reset itself whenever there is a vibration or movement on it. Upon close inspection I found the adapter port is loose which triggered the switch to loose power for a few miliseconds and enough to cause it to reset itself. So I fixed the faulty switch unit and after that I no longer see eth1 from having glitches in the log file and so far my Deco X60 has been working fine without any WiFi speed issue for the last 2 days.

If I didn't login to the unit directly via web browser I wouldn't have picked up this issue as the mobile app never show the constant change between ethernet backhaul and wifi backhaul. As far as what the app showed everything is in fine condition and there is nothing to worry about. So I hope this post help people to realise that in order to troubleshoot your Deco or any router issue you need to go through the log file and decipher what has gone wrong.

As to why only my phones are impacted and not my family phones, I am at a loss to figure out why. The only thing I can think of is I carried my phones with me constantly whenever I move between rooms in the house whilst my family tend to leave their phone in the room or not move around the house as much. So perhaps my actively roaming phones are the ones that suffered first.