I have the E4 and only one device seems to disconnect randomly throughout the day from the wifi network comes back eventually though. 

I happened to be in the same room on my device when my family member moaned as she thought i turned the wifi off but ofcourse  i hadnt.

My deco's are in Access Mode with the Main router still inuse as i need bandwidth control which the E4's appoach for this wasnt good enough.

All connected by Ethernet as shown in the app. They are always showing as "Online".

Currently: Disabled Fast Roaming and BeamForming.

I do have a Guest network Also in effect but that cant be why this one Device drops surely?/  The user is has the passwords to both Network SSIDS and no matter which wifi shes on it will drop.

TDLR; Mum going mad at me. IDK what to do as i can't find a fix as i believe i have tried every configuration for this deco