Ensure your playback setting is set to "Sync to Audio" (found in the Timeline header under the Playback menu). If it's set to "Play Every Frame," your animation may drift and look out of sync during preview.
bridge the gap between spoken audio and visual mouth shapes (visemes) mapped to a character rig auto lip sync blender
Stop Manual Keyframing: The Best Auto Lip Sync Solutions for Blender Ensure your playback setting is set to "Sync
The Ultimate Guide to Auto Lip Sync in Blender: Animation Made Easy auto lip sync blender
are great for video-to-video translation, using Blender’s native tool gives you total control