@Mac3 

Hi, Have you tried to update to the latest firmware：

Deco X20(EU)_V2_210424

(You might need to log into the web interface of Deco X20 and upload the firmware.)

In case it is not working, could you please help me check the following information so that I could forward your case to the senior engineers:

1. Can I have a picture of the floor map about the Deco system, especially the location and distance between the Deco unit;

2. If putting the 3rd Deco X20 next to the 2nd one, would it link to the 2nd Deco? 

--if yes, after removing it back, would it still link to the 2nd Deco, or back to the main Deco?

Thank you very much and wait for your reply.