@Lilyinthevalley What's your deco region code? EU or US ?

@Boeau I think all the issues are related to subnet mask because some IoT devices and phones could'nt support 255.255.252.0 subnet mask so you can change it to 255.255.255.0 because newer deco models...

@windqsp I mean have u checked the speed before and after plugged ethernet cable on Deco? is there any difference in speed?

@windqsp Have u checked the speed before and after connect the ethernet cable to Deco on your laptop or phone?

@Ashrobo Have u connect the Deco 3 from Deco 2 by using Connection Preferece? Because by default Deco can connect to only Main Deco (1)

@DukeCaboom Try to change the adapter.