Sorry for the confusion - we run a WiSP service for a large rural area using Motorola Canopy radios (not 802.11) - over 500 customers, many commercial gas production facilities, coal mines, etc. The radios have MAC's starting with 0a-00-3e… When NAT is turned on they change the first number to a 2 (2a-00-3e...).
Again, I got this sorted out. I know what the messages mean, and I use them regularly to monitor duplicate IP addresses being used, but there was an issue with our syslog server and the messages it was sending out to us (only sending the first message multiple times so it looked like same change was happening multiple times, instead and back forth between the hosts).