This is more of an issue with CEC. I had it working great, but now when I turn off the TV via the ATV remote, it comes back on within 30 sec. I turn it off again and it stays off. If I turn it off with the Samsung remote, everything works fine.
Almost looks like the ATV sends an on signal after shutting down when using its remote. The only way to fix is to disconnect everything including power, turn it all back on with no HDMI cables connected, then reconnect everything one at a time.
Or just wait for the next TVos update to cause a different issue.