Hello guys... i'm running almost in the same issue here.
The difference I see is in my case, both ip address i'm seeing are valid. we have our scopes splitted in 2 dhcp servers... one physically local on each site and one remote across the wan.
80% of the duplicate ip address are from a valid dhcp server (either local or remote), rest of them are ip address outside our known IP range.
I tried the "enforce dhcp", but since both ip address came from a dhcp sever it dosen't look like did any difference. Any idea of what could cause this?
Thanks for your comments.