Audio problem: When Tori fake hits Jade, the sound doesn't match up.
Audio problem: When Tori is on the stage singing, Robbie walks up to Tori and says "I deserve it!" When he says "ow!" his lips don't match.
Audio problem: After the Robarazzi crew take pictures of Tori's armpits, in the next scene and many scenes after that, when they talk their lips don't match.
Audio problem: When they start to sing the favorite food song, you can obviously tell they are lip syncing. If you look right when the kid starts filming them with his cell phone, you can hear Tori singing but her lips aren't moving.
Answer: The Director hated working with Melinda, but knew that her superstar popularity and status would get his movie a big buzz and higher ratings. And the movie was discontinued for a re-audition to fill-in Melinda's leading/major role.