@SimonKrogh 

 

It is possible that one of your neighbors created WiFi network with the same SSID as yours, and your device tried connecting to their WiFi network. This could have been mistake on their part, a prank, or an attempt to trick you to reveal login credentials to your WiFi network.

 

If you are concerned about security of your home network, in Deco Main Network configuration enable "Hide this network from WiFi lists," change Network Name (SSID) of your home network to something completely different, make all your mobile devices forget old SSID and connect them to new SSID only you know and nobody can see when they scan for WiFi networks nearby.

 

This will protect from most hacks or pranks, where someone tries to impersonate your WiFi home network.

 

I don't think that's likely. Most of my neighbors are senior citizens and I don't see how resetting my own units should fix the issue if the SSID has been spoofed by people from outside.

  @SimonKrogh 

 

Someone hacking into your Deco M5 is also unlikely. Next time it happens, if it happens, take screenshot of that login screen, it might give an idea what it is your device tries connecting to. 

 

My ISP router, for example, presents login screen for its Guest Network. So do many public networks. What you have seen might have been your device connecting to one of those WiFi networks it remembers, instead of Deco. Also, as I said before, could have been one of your neighbors setting same SSID as yours, and then changing it to something else.