I have found in releases after 378.56_2 repeater mode has issues if there is a device plugged into the switch ports. On a couple repeaters I have I used the ethernet ports for network attached cameras and on these repeaters DHCP requests don't return to clients. I see the request make it to the DHCP server and the server respond but the wireless client never gets the response. Unplugging the device from the ethernet port on the repeater immediately fixes the issue and request route properly...
Repeater mode on RT-N66U with releases >56_2 not rotuing
Repeater mode on RT-N66U with releases >56_2 not rotuing