Roku Streambar SE turns back on at some point after powering off

Just got the Streambar SE (love it!) and have it connected to my older Vizio TV via HDMI-ARC.

The power button on the Roku remote successfully powers off both the Streambar and TV, but the next morning I notice the Streambar is powered on (the LED is lit), but the TV is not. I then press the power button on the remote, and the Streambar powers off (and the TV remains off).

Did I get a lemon, or is there something I need to check in TV or Roku settings?