2nd router address on single SSID?

I am having a problem where a few of my devices do not have web connectivity over Wi-Fi when most of the rest do.  I notice all the devices that have a connectivity issue show a router address of 192.168.48.1 and the device have an IP address of 192.168.48.xxx.  However, the working devices are point to 192.168.0.1, which is the correct address I see when I log into the gateway.  It seems like the Cox equipment has a second router that does not fully connect to the web.  

I also see that sometimes my iPhone starts with a correct IP address and then it changes in an hour or two to a bad address.

One final complexity is my phone still connects to Apple Music and is able to stream music with the 'bad' IP address, but most other apps have not connectivity.

I can manually enter a correct IP address but would like to understand what's going on.  I've done all the possible resets and unplugging multiple times and even gotten a new gateway from Cox.  The issue persists.  Any help is appreciated.