@Jonchill It is possible that some sort of WiFi signal interference had been introduced, such as new microwave, fridge or cordless phone. Also that interference might have been coming from your...

@tiboc I would recommend NOT to make Deco X50 Outdoor your new Main Deco. When you add it to Deco mesh, Deco app might even suggest to make X50 new Main Deco, you should decline that suggestion. With...

@tiboc Do you plan to place Deco X50 Outdoor outdoor, or you plan to keep it somewhere in the house? Also, do you run Deco mesh in Router mode or in Access Point mode?

@berne Yes, it will be the same network, and from what you described it'll be 192.168.0.* network. You do not need to change the connection, in your case it'll be the same for both current Deco...

@bobby0724 1. Do you have smartphone to run speed tests on? 2. Are you getting these speeds (250Mbps) from Main Deco or from Satellite Deco?

@berne You need to configure Deco mesh to run in Access Point mode. See Switching a Deco to Access Point (AP) Mode