I took a look at that code and it appears to be superfluous, perhaps something I copied from Steve Wright's APC UPS Monitor Driver. The deviceNetworkId field is not used by the remainder of the code.
I'm wondering: other than the UPS does anything else on your system send a message to the laptop's Event Ghost port? Also turning off the debug flag should stop those messages.
So @sburke781 thank you for reporting this issue, and @FriedCheese2006 thank you for confirming the solution. I'll update the code in the near future.
Comment out this code.
// Update DNI if changed
if (msg?.mac && msg.mac != device.deviceNetworkId)
{
if (enableDebug) log.debug "Updating DNI to MAC ${msg.mac}..."
device.deviceNetworkId = msg.mac
}