Devices pulling invalid IP Addresses and losing connection

The CM1000 is a "plain modem".  All it does is interface between the coax cable system and the ethernet router system.

What is supposed to happen is the Orbi asks for an IP address and the cable system returns a "public" IP address for the Orbi to use.

This will be found on the Orbi web interface, http://orbilogin.net.  Click on the "Advanced" tab and the "Internet block will show this public IP address.

The Orbi assigns "private" IP addresses to every device that asks for one.  This is controlled on the Advanced Tab, Setup, LAN Setup.  Normally, the Orbi assigns itself the address 192.168.1.1 and gives out addresses from the "pool" to devices.  (There is a method to assign specific IP addresses to individual devices on the LAN setup page as well.)

If some devices are getting private addresses that begin with 172.16, then there is another device on the network that is responding to DHCP requests.  Perhaps the new entertainment center has an option to act as an address server?

My suggestion is to turn off the entertainment center (the last thing added to the network).  Turn off the CM1000 modem and Orbi.

Turn on the CM1000 and wait for it to "settle down".  Turn on the Orbi, and see what happens.  If everything returns to normal, it's time to check into the entertainment center configuration.  (I would say, "slap it upside the head", but that reflects badly on my red nect roots.)