Continuity: When Nancy drew is talking to the guy about the records for adopted children the cake she gave him keeps appearing and disappearing off the napkin as the shot changes.

Deliberate "mistake": In the facial morph, the faces don't come anywhere close. The face was morphed with no feature of either resembling the other. The only matching features were the hair and neck which were not touched by the morph. The midpoint of the shift wreaks of Photoshop-like effects (softening of the face alone).

Other: When Nancy finds the trapdoor from the attic, she goes down a ladder and gets onto the other floor. She walks a bit and goes down another ladder then looks up and Ned throws the flashlight straight down to her.