Max3
4
This also happened to me, and it happened A LOT of times even on old UI using Mango, Creta and Beryl.
When assigning static IP and Hostnames, at some points the system showed the same IP for 2 particular devices.
On old UI, I fixed it deleting tertinfo from vart/tertf/tertfinfo, deleting static IP from GLUI, assigning IP and hostnames manually in etc/config/dhcp and rebooting both router AND the devices affected.