Hi, 

i have 3 deco S4. one in the corner is our main router, one in the dining room and one in my office. 

Connection between the middle and main has dropped to just one yellow bar and is causing the bandwidth in my office to be very very low. 

There is no more than 10 meters between the main and the middle deco, however there are a zigzag of brick walls. I have a spare M3W and tried putting in between the main and the middle but it was always connected to one of the S4's not bridging the gap.. is this not possible? would i have to get a 4th S4?