Hello, I bought 6pcs (2x 3Pack) Deco E4 and currently using 5 out of 6.

But somehow every now and then the 2nd Set of routers gets disconnected from the Network. 
Here are the things I do to get it resolved.
- Sometimes it get's solved by restarting the main router
- Sometimes it gets resolved by re-adding the router to the network

is there anyway to prevent this from happening again?