WISP repeater mode troubles


I bought a mini router Ar300M (a truly exceptional product!) to use as WISP repeater connected to a public wireless network. The main router has an IP address range 192.168.1.xxx, mini router instead uses the 192.168.8.xxx range. Well, everything works perfectly, but if I check the devices connected to my LAN in the AR300M router web UI I find sometimes in addition to my devices (with IP address 192.168.8.xxx) and the main router (with IP address 192.168 .1.1) another unknown device with IP address 192.168.1.xxx, that I guess it should not be there. How do I avoid this?

Thanx in advance

P.S.: For now, waiting for some suggestion, I disabled Wan access port and added unknown device to MAC filter blacklist.

the ip addre3ss 192.168.1.x should not in the list of AR300M. But the UI does has a bug that it reads all the connected devices, no matter from WAN or LAN and displays there. Actually these 192.168.1.x is not in the subnet of AR300M. If you don’t mind just ignore them.

Thank you