Audio problem: Having reached her house after running home in the rain, Sarah's stepmother stands on the porch and we hear her say, "Oh, really," but her mouth does not move at all. (00:04:45)
Audio problem: In his throne room, Jareth starts to sing, "Dance, magic, dance..." In the overhead shot when they sing the words, "Put that magic spell on me," he kicks the little guy up, then in the next front shot when he sings the second line, "Jump, magic, jump," and just before and during which he throws Toby in the air, in all these shots either his lips do not reflect the words heard or his lips move and no sound is heard. (00:23:55)
Audio problem: When Sarah meets Hoggle, while exterminating fairies, she says, "You're horrible," but her lips do not move. (00:15:55)
Audio problem: When in the Goblin's house, Sarah chucks a plate of food in a Goblins face and says 'Hungry?' but her mouth doesn't move when she says this. (01:20:05)
Audio problem: At the Bog of Eternal Stench, as they start to walks across the rocks in the bog, Didymus says "Steady, steady boy. Come on Ambrosius! Just close your eyes, and go!" His mouth doesn't move at all when this is said though. (00:59:50)
Audio problem: In Jareth's throne room, Sarah says, "That's the only way he could have gone," then says, "No! No!" Her lip movements do not match the words we hear. (01:26:45)
Audio problem: Watch Agnes the Junklady's mouth as she picks up Charley Bear. The second time she says Charley Bear before putting it on Sarah, her mouth doesn't move.
Answer: The necklace is a symbol of Jareth's power throughout the story. All the time that Sarah is in the Labyrinth, Jareth has more power than her, because she doesn't really know what she's doing, and isn't taking one particular path, just getting lucky at the right times. At the end, as we all know, Sarah triumphs, and Jareth's necklace changes to admit his defeat.