Continuity mistake: As Annie leans up against the middle of the red mailbox she knocks the flag down. When we see her again her right arm is pushed up against the front of the mailbox and some amount of time, longer than the three seconds implied, has gone by as the shadow of the mailbox's handle moves between shots. (00:18:00)????
Revealing mistake: As Lydia talks on the phone Mitch walks into and out again from the kitchen and you can see his shadow fall on the drapes to the right of the dining room table. Later on Cathy goes into the kitchen and right after Mitch sits on the piano stool look closely at her shadow. Though not as prominent as Mitch's it can be seen in the same place for 20 seconds as she waits for her cue to enter the dining room. (00:34:00)????