Audio problem: In the beginning, Claudette and the other counsellors are all singing. When they get closer you can see that Claudette is playing the guitar, then she stops, but the guitar playing and singing still continues. (00:02:10)
Revealing mistake: When Steve Christy is leaving the diner, it shows the outside of the diner, where it is raining. It's very obvious that the "rain" is just a sprinkler.