You can demultiplex the vobs, load the files in dvd-lab and use "tool > audio delay" to sync the audio to the video. Dvd-lab will make a new audio file synced to you video. You can use the video file and the new audio file to rebuild the dvd (dvd-lab also allows negative delays).
EDIT: I hope the difference in sync is the same troughout the movie otherwise this won't work.