Some VOB files need extra information to be played correctly. Therefore you'll normally found there are some other files on a DVD rather than just the VOB file.
If you play these VOB file alone on a player, the player would probably try to guess the missing information and recover from error. Even the video can be played, there will be other errors like A/V out of sync or no seeking etc..
To fix this issue, we will provide an option to generate a new video with recovered information. It might still have issues like audio out of sync etc..