DHCP server bad address issue

Hi,

I'm having an issue with ip address conflict or "bad_address"

I've checked for rogue dhcp server with wireshark. One issue i'm having is that the mac address of the device getting the bad_address issue on the dhcp server is only 8 characters. There is no such device like that on my network. This would be occuring every other week. Removing it solved the problem, but how do i find the culprit of this problem?

Thanks.