I have been using five (!) Deco P9 since a year or two but have been struggled with a seriously unstable wifi experience ever since. Latest firmware, moving them around, install/uninstall, set up every single one of them as the main router, trying different options (there ain't many), etc, etc. My connection goes down multiple times - every day, every hour! if I'm lucky, three of them will work simultaneously BUT then my devices seems to prefer to connect to the ones not working. 

I have a stable (yes) 100/100 mbit fiber in my house. Using my TP-Link Archer AX73 router everything works great but then there is a reason I bought the Deco in the first place, one router just won't cover everything. P9 also transfer data using powerlines they say, that's what really got my attention.

When they work, it works! Everywhere! But why do they disconnect all the time? There have been no more firmware releases for many month, is P9 a dead end? Should I go for the AX73 and OneMesh extenders instead?  

Edit. Deco units blink red, unplug and plug in and they work for a few hours/days again. All units disconnects randomly it seems.