@ClaudioT 

Connect your computer to the second LAN port of the main Deco unit. What speed do you get that way?

Alright, I've tested with a direct Ethernet cable plugged into the main Deco and I'm getting the same speed 3-6Mbps

@ClaudioT 

Swap the main Deco unit with another of the satallite units. Do the speed test with the computer one more time, make sure the computers Wi-Fi is disconnected.

With respect to the testing of the Deco app it may give incorrect information, and having the satallite units too far will affect the speed.

If swapping the Deco units does not show better speed you can try factory defaulting the deco units and setting them up again. If in the end they are still showing slow speed it would be best to contact our suppot to see if they may have software available to assit with your issue.

I'm having the same issue, and have tried all the troubleshooting as described. Even tried changing to an ethernet backhaul to see if that helped.

I'm on 1000mbps internet, but the Deco app speed test gets about 500mbps, and when running a speed test on a wireless device it is maximum 30mbps, often dropping to 2-3mbps.

Prior to the latest firmware update, I used to get wireless speed in excess of 300mbps.

Just killed the 2.4ghz network, and that improved things greatly. 150mbps on wireless now (5ghz). For whatever reason, all devices capable of 5ghz were choosing the 2.4 network. This createds a minor complication as I have devices that will only connect 2.4 (such as my Ecobee). I have to run a separate 2.4 network from my internet router to handle this.

Part of it may be that the m5 is a dual band system without a dedicated band for backhaul. Unless youre connecting the decos via ethernet?

Matt2100 wrote

Just killed the 2.4ghz network, and that improved things greatly. 150mbps on wireless now (5ghz). For whatever reason, all devices capable of 5ghz were choosing the 2.4 network. This createds a minor complication as I have devices that will only connect 2.4 (such as my Ecobee). I have to run a separate 2.4 network from my internet router to handle this.

Perhaps, but that doesn't explain why it was working fine before.

And for that matter, even with ethernet backhaul it was still slow, until I killed the 2.4 network.

And, now as I type this and tried a speed test, I'm only getting 35mbps on 5ghz on ethernet backhaul to a 1000mbps connection. Direct to the router, all with cat6.

Something has changed, and performance dropped. 

Matt2100 wrote

Just made a discovery: Checked my router, and it indicated one of the ports was only connecting at 100mbps. I checked which M5 puck that corresponds to, and it was the one I was connected to. I walked to another part of the house so I would be on one of the 1000mbps connected pucks, and got 200mbps wireless again. So, I disconnected the slow one, and it connected via the unused 2.4ghz radio (so, it will run a mixed topology!). Got 100mbps speed now on wireless (vs 40 before). Great! But why slow on ethernet? I plugged it back in to ethernet, it linked at 1000, and got the same 200 speed as the others, but after a few minutes it dropped to 100 on the wire, and wireless back to 40.

 I’m not sure. I would just return the entire set and exchange it for a new set maybe there’s a bug. 

@ClaudioT 

I have 2 Deco M4s and am finding after about 30 minutes of a full restart the speed drops form 200Mbps to 9.5 Mbps.  This is on cabelled and Wifi connections to the main Decos's second port.  After talking to support I was asked to swap the man and slave over, this of course worked as it was the equivalent of a restart.  They went off all chuffed they'd solved another issue....  20 minutes later and my internet on all devices is crap again.  Prior to this all devices worked great except for dead spots in the house.  Now I have no dead spots but everything runs at 10 Mbps and devices drop out / games loose network connectivity (I assume this is when the device changes wifi from deco to another deco?)  I set almost all device barring mobiles and tablets to not roam between access points which helped.  All I want now is to refund this pile of crap and go back to my crappy Virgin Hub 3!!  Dead spots are great if this is the alternative!