Hello friends. I have 6 Deco XE75 Pro devices at home. They work very well. I have approximately 60 wifi devices connected to this network, they all work very well. There are areas of my house where I don't have good coverage. To improve coverage I bought 3 other Deco X55 devices. The problem occurs when I add any of the 3 Deco X55s to the existing Deco XE75 Pro network: the entire network becomes unstable. More than half of the devices cannot connect. I have updated firmware but nothing works for me. It is as if a channel conflict is generated. 

Everything returns to normal when removing the Deco X55. The Deco X55 works without problems when alone (not linked to XE75 Pro)

can you help me?