Audio problem: When Lisa visits Homer at the plant, they are playing astronauts with the radiation suits. When they spin around and around, Homer is laughing but his mouth stays the same.
Audio problem: When the car drives into the cornfield, Martin is heard screaming, even though he is still asleep.
Answer: I'm not sure if this is the one you're thinking of, but an episode of "Ray Bradbury Theatre," called "A Sound of Thunder," dealt with a similar matter: a group of hunters travel back in time to hunt dinosaurs, only to find things have changed when they get back because someone stepped on a butterfly.
Xofer