Monique wears a black belt in her room in the scenes before and after the park. At the park, she wears a black and silver belt. The two scenes were shot 8 days apart, which explains the error. This isn't very obvious since Monique is sitting down in the park scene.
Though it's not really visible, there were some small Halloween decorations on one of the condos during the shooting of the scene outside Amanda and Dan's condo (near the end of the film). They can only be seen if the movie is played back slowly. The film was shot in October, but since it takes place in July, the cinematographer had to take care when shooting. It wasn't possible to have every owner remove their decorations.