Claudia and the Secret Passage - S1-E8
Stupidity: The fact that Kristy found the ring that was missing for 40 years just sitting on a windowsill in the secret passage makes no sense; Dawn and Claudia were just by that window earlier in the episode in broad daylight.
Suggested correction: We don't actually see where Kristy found the ring; it was dark, and the girls were chaotic.
Other mistake: We know the girls all go to school together, but when they are walking home in the opening scene, they all meet up coming from different directions.
Suggested correction: They don't approach from very different directions. All of them are still basically in the same area of lawn and trees. This is possible depending on what they do after exiting the school building. Maybe someone walked in another direction so they could briefly talk to other friends, etc.
Character mistake: At the end of the dance routine, all of the girls strike a pose with one hand on their hip and the other behind their head, except for Stacey who just stands there.
Suggested correction: Stacey was in New York with her father for most of this episode, so perhaps she didn't learn the entire routine before performing it.