Quantum Gateway Router.
Got a 4k Apple TV and the problems started.
Prior to connecting the Apple TV, I had TiVo and an external hard drive connected dircelty to the router via Ethernet.
I plugged in the Apple TV and the Wireless networks turned off then reappeared but the passwords did not work. (even though they were being provided by my phone's memory.) Then the rest of the Ethernet connections did not work either including my TiVo.
Unplugged all LAN connections and the wireless worked again. Did a factory reset of the router and set it back up...plugged in the TiVo and the wireless connections went away.
Unplugged it and its fine.
Holding for verizon for 30 mins....
Try a factory reset of the AppleTv.
Sounds as though it is interfering with your ethernet operation.