DIAGNOSIS This lip-sync error happens because your TV is doing extra video processing that takes time, but the audio arrives at the soundbar instantly. They fall out of step.
FIX First, check your TV's settings. Look for a setting called 'AV Sync', 'Lip Sync', 'Audio Delay', or 'Digital Audio Out Delay'. If you find it, adjust it (usually increasing the delay number) until the sound matches the mouths. If your TV doesn't have that, the next step is to try a different audio format. In your TV's sound or external speaker settings, change the 'Digital Audio Out' format from 'Auto' or 'Passthrough' to 'PCM'. This often eliminates the delay because it sends a fully decoded signal.
IF THAT DIDN'T WORK The Bose app has a manual adjustment. Open the Bose Music app, select your soundbar, and go to 'Settings' > 'System' > 'Lip Sync Adjustment'. You can manually add delay in small increments here. Play content with clear speaking and tweak it until it's in sync.
HEADS UP This problem can be source-specific. The delay might only happen on your built-in Netflix app but not on your gaming console. If so, you'll need to adjust the sync setting for that specific source, if possible, or use the Bose app adjustment as a universal fix that works for everything.