We finally upgraded our beta unit to latest firmware (GWN7600 SW 188.8.131.52 to 184.108.40.206). We upgraded it, and had a short bug, but it was fixed via factory reset. Just bringing it up here for future reference.
Under System Settings -> DHCP Server, there was an enabled, DHCP server with leftover settings. We couldn’t disable it because the “DHCP Gateway” is blank. Factory reset solved the problem, but in case anyone else has this issue, there seems to be no work-around.