why does my vizio m512a-h6 keep switching sound modes on its own when i'm watching a movie

DIAGNOSIS The soundbar is reacting to the incoming audio signal format and auto-switching its DSP mode, which is an intended (but annoying) feature.

FIX Disable the auto-switching by manually locking in a sound mode.

1. Use the remote or the button on the soundbar to cycle to your preferred mode (e.g., 'Movie', 'Direct', 'Music').
2. Once selected, press and hold the 'EQ' button on the remote for 5 seconds. The display will show the mode name and then 'Save'.
3. It will now default to this mode regardless of the input signal.

IF THAT DIDN'T WORK Ensure your TV's audio output is set to a fixed format like 'PCM' or 'Dolby Digital' instead of 'Auto', as constant format changes from the TV can trigger mode switches.

HEADS UP Manually saving an EQ mode also disables the 'SmartCast' audio tuning feature, so you'll lose any room calibration it performed.