@allibhai 

Start with this: What can I do if the internet connection is unstable when connected to the Deco network?

Thanks @Alexandre.   - case 3 sittuation 2 applies to me, but fast roaming is already disabled In terms of the questions: Identify issue is can’t connect to deco or connected but no internet when the issue happens.- Wifi is connected, but there is no internet How often did this issue happen? - Every few hours Collect Network topology. - as above

 @Alexandre. interestingly I just had another wifi drop out just now at 18:50. This time however, the light on my Sattelite Deco M4 was flashing red. I then went downstairs to see what the sittuation was, but when I got there the yellow light was showing, which then became red, and then blue

Now the wifi is back up and running. I am very confused by what is going on!

  @allibhai 

See this document: What do the different LED colors meaning of Deco?

The only way I can think of why healthy Main Deco M4 may show Yellow light is it was powered off (lost power) and then you saw Yellow light when it was powered on and coming back online. 

Main Deco powering off/on could explain Internet connection dropping for all devices in the house and Red blinking light on Satellite Deco. 

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Check electrical wiring, electrical socket and how Main Deco is plugged. The problem might be there.

  @Alexandre. I can confirm there is no issue with the electrical wiring - there are a number of items connected there and it is only the Deco that is having issues

  @allibhai 

If you have Main Deco connected through extension cord or power bar, I would suggest plugging it directly to the electric outlet instead. To see if it makes a difference.

The only other possibility I can think of is your Main Deco experiences hardware failure, which forces reboots. To check that, swap your Deco units, by promoting your Satellite Deco to Main Deco. Here is the process: Changing the Main Unit for your Mesh Network

  @Alexandre. Thanks - have tried swapping one of the sattelite decos with the main deco. Will report back

  @allibhai How many online devices do you have? I experience the same over 10 devices. Deco keeps dropping connections as you hit the limit of 10.

  @allibhai This did not work, still having connection issues