@Pierwitch How many Deco E4 units do you have? If more than one, do Satellite Deco use WiFi to connect to Main Deco, or you wired them with Ethernet cable? Deco E4 hardware specifications:

@Pierwitch Deco E4 has 100 Mbps Ethernet ports. As long as you keep E4 as Main Deco, 90 Mbps is the fastest speed you can get.

@Kabnine Not every brand of WiFi mesh allows to configure how satellite nodes connect. That was the reason for initial pushback from TP-Link Deco development team: "Nobody does it, so why should we?"...

@Ljunganz TP-Link Deco is more limited in that respect. As you can see from Deco app, you can have one Main Network and one Guest Network. That's it. If you are not using Guest Network for anything...

@Flatret Let's cover all bases, which are: password with special symbols, dual band steering, WiFi mesh. For older WiFi devices it is usually one of these three. 1. Password. Turn on Guest Network in...

@Kabnine I have not seen TP-Link providing updated Deco firmware for X60 to choose how Satellite Deco will connect, but in your case there might be a workaround. It depends on what is Main Deco...