I have another issue with Tp-link Deco M4
the past week I only use one unit (living room)

1) yesterday when I set up the second unit at 1st floor (main bedroom) 
it couldn't found any my main deco (ground floor - living room)

2) after following the suggestion from tp guide, I put the second deco at  my main deco (ground floor - living room)
The connection was successful and manage to add my second deco.
 

So i plug out my second deco and put it back at 1st floor (main bedroom), now my led turn into [COLOR=red]BLINKING RED[/COLOR]. As per TP-link deco suggestion, they ask me to reset. But then it loops back to my point number 1.

Before this, by only using main deco (living room) -  I still manage to get internet connection if I'm staying at 1st floor (main bedroom)

Any suggestion?