It is the same with me too!
samba_dlz: spnego update failed
dhcpd: unable to add forward map
samba_dlz: starting transaction on zone zentyal.lan
named[5293]: samba_dlz: spnego update failed
named[5293]: client 127.0.0.1#30910/key zentyal.lan: updating zone 'zentyal.lan/NONE': update failed: rejected by secure update (REFUSED)
named[5293]: samba_dlz: cancelling transaction on zone zentyal.lan
named[2303]: samba_dlz: spnego update failed
dhcpd[2135]: Unable to add forward map from android-4983c6d6daf4ed4c.zentyal.lan. to 192.168.2.108: REFUSED