I just installed a three-pack of new M5 mesh WiFi devices on my existing home network. The modem / router / WiFi combo is the Xfinity (Comcast) XFi system - brand new. I'm running Ethernet cable to each M5. During set-up of the first M5 it required me to create a new home network - very weird as it should have just used my existing home network, connected to it, and extended the signal throughout the house (2-story). After following the set-up instructions and creating the new home network, the first M5 joined and connected just fine. The second M5 was also plugged into Ethernet which is hardwired to the XFi (modem/router/WiFi) seems to join just fine, but it joined to the new M5's home network instead of my original home network. After this I noticed my original home network disappeared, then the new M5 home network dropped, and 5 min. later came back online for about 2-3 min., then dropped again. I don't want to reassign all my home automation smart tech to the new home network. That's just stupid. 
 

Since I WFH, and require stable reliable high-speed internet, I unplugged both M5's from power and Ethernet ports. Then my original home network magically reappeared and reconnected to all my smart devices & computer. 
 

Before I completely bail on this M5 mesh system, I'd appreciate someone suggesting a better way to connect the M5s so it actually just "extends" my original WiFi from the XFi unit to all parts of the house where I have Ethernet & power specifically for this purpose. 
 

Side note, I've had excellent experience with the ORBI mesh 3 device system, but this unit - not so much.  Thanks in advance for any assistance.