said by JoelC707:No idea how I would change the DUID (though I can certainly look it up), and even so I can't see why it would change. I am spoofing the WAN MAC to maintain my original IPv4 address after I changed hardware for the firewall a while ago. Maybe somehow the real MAC is coming though but even still, there's only one real and one spoofed MAC so I should theoretically only see two different PD prefixes? This makes the fourth PD prefix I've seen in just two days.
Or pfsense lost, gained, changed an interface and is using that interface to base the DUID. Wish you could specify a static DUID (for dhcp6.conf) in the pfsense interface.