This computer's local hostname is already in use on this network.

Recently, Xfinity texted me and asked me if I wanted to accept the free upgrade of my Internet gateway to the newer and faster version. I accepted and they send it to me. The automatic set up process seem to go smoothly, but now I am starting to get these messages:

This computer's local hostname

"Timothys-Mac-mini-3.local" is already in use on this network.

The name has been changed to

"Timothys-Mac-mini-4.local".

I accepted the message thinking it was a one-time thing, but today, when waking the Mac up from sleep, I got the message again. Is this normal, is it going to be a regular occurrence, and is there a simple way to stop this message from popping up repeatedly?