Harry Potter and the Prisoner of Azkaban - Time Mix Up!
In Hagrid's hut when Hagrid gives Ron Scabbers, Ron says, "Scabbers! You're alive!" Then about 10 seconds later, a rock gets smashed into the vase. But when Harry and Hermione go back in time, Ron says, "Scabbers! You're alive!" And then, it is almost a minute later when the rock hits the vase.
The whole point is that there is supposed to be a time delay. Hermione and Harry are waiting for them to come out, but don't realize they have to throw the rock until Hermione notices that Dumbledore's coming and they aren't leaving. When she sees the rock then she picks it up and throws it. Hence the time delay. She didn't realize what she had to do. It was the whole point of going back in time that things would be different. They were there to change things!