A common copy protection technique is to load many titles on the disc and a program like Handbrake will often have trouble locating the correct one, and you can end up with video with no sound, mixed up video, cut short, etc…
To correct this issue, start playing the movie in your computer's dvd player. When the main movie starts playing (after previews, etc…), see which title is playing. Then you tell Handbrake to rip this title as the main movie.
If you are using Apple's DVD Player, go to the top with your cursor to show the menu bar, then go to Go → Title. The correct track should have a checkmark.