Some owners of the fourth-generation Apple TV are complaining that the device is spontaneously waking up itself and/or connected TVs, an inconvenience that could burn unnecessary electricity and could potentially cause screen burn-in for people with plasma sets.
The issue is the subject of numerous threads on Apple's support forums, and can also be confirmed by AppleInsider. Affected people may see their Apple TV turn on as quickly as a minute later, though longer delays are reported as well.
TV sets with HDMI-CEC support will turn back on as well, wasting electricity and potentially disrupting sleep. Plasma burn-in is a risk because tvOS may not always run its screensaver as it's supposed to.
The exact cause of the problem is uncertain, with owners blaming everything from Bluetooth to AirPlay. Some people have reported success in closing some (or all) apps before putting their Apple TV to sleep, or else restarting their unit first, or even turning off ad tracking. Those just concerned with keeping a TV off can disable HDMI-CEC in tvOS settings.
Such solutions would suggest that the problem is rooted in a software bug. If so Apple could fix it in a future tvOS update, but there's no immediate sign a patch will be wrapped into tvOS 9.2.