@drogue THIS HAS WORKED FOR ME ALL DAY SO DAR WITHOUT DROPPING A CONNECTED DEVICE.

I had the same problem..

with Deco XE75  / XE75 PR0

I REFORMATTED OR RESET THE DECO DEVICE AND RE-DID THE FULL SETUP.. 

>>> I ENTERED MY OLD SSID AND PASSWORDS <<< FROM MY ORIGINAL ROUTER. 

FOR THE MAIN NETWORK 

I USED MY 5G SSID & PASSWORD.

I WENT BACK INTO THE APP AND CREATED A GUEST NETWORK 

SET THAT ONE UP AS 2.4 ONLY 

>> WITH MY SSID AND PASSWORD FROM MY OLD ROUTER <<

I SET MY MAIN NETWORK IS 5G ONLY DOING THE SAME 

AND RE-CONNECTED ALL MY DEVICES INDIVIDUALLY

I ( DID NOT DISABLE ) BEAMFORMING 

I HAVE NOT HAD ANY ISSUES WITH DISCONNECTING AND CONNECTING CLIENTS