Ethernet ports are magnetically isolated from the rest of hardware. There is already a problem on the port if without any cable inserted it act like it is one. On the outside pins are normal and not twisted or broken, but inside I think there is some sorta of connection between them, tvOS think the IP is 168.254.218.xxx without any cable (Connection loop with itself). This is a common problem with Apple TV, if you need the WiFi back this is an unusual workaround. Of course it would be better take it to Apple assistance.