Phantom AirPlay device named "Apple TV (2)"

Apparently I'm seeing a neighbor's Apple TV via peer-to-peer AirPlay. So they're not on my Wi-Fi network but don't have to be.

• http://forums.macrumors.com/threads/macbook-ipad-sees-atvs-on-neighbors-wifi.1887338/
• https://www.reddit.com/r/apple/comments/33j6yn/multiple_apple_tvs_showing_up_over_airplay/

This is annoying. Now I'd like to know how to disable this (it's particularly annoying when trying to change the volume via the menu extra since the slider moves from under my mouse after a second), but it seems impossible to disable this mis-feature.

• https://discussions.apple.com/thread/7723176
• http://help.apple.com/deployment/ios/#/apd8fc751f59