I tried almost everything one could imagine to get the X60 to not disconnect every few hours after recycling it. No matter what, two of the six X60s will go offline for no good reason. And the clients will disconnect so often. my iphone does "Cannot connect to Internet do you want to switch to CellphoneI even reapplied the latest firmware on all the devices, shuffled them across rooms, changed QoS settings, Beam Forming settings, Quick roaming settings, Port forwarding settings and every single thing that was available as an option. I even hard reset the devices individually by holding the reset button for 20 seconds. Nothing helped. 

Few things to note: I had moved to a different country, and combined two or more X60s that were on a different network into the new network. All X60s were backhauled- none of them were wirelessly connected with each other. 
 

Finally, I created a brand new TP Link account with my new country as location, reset all the X60's and created a brand new network and connected all of them - it was a pain factory resetting each X60 and adding them to a new network - but it was worth it. After this, there are no network drops, no X60s going offline nothing. 

I have no clue why this creation of new account and creating a new network would solve the problem I don't have any clue. 

Just in case if this helps anyone!