Two continuity errors occur twice in the final scene, when Mary sings "Big Star." Before she begins singing, we see Mrs. Stone retire upstairs for the night and as Mary leaves the house, she turns off the lights leaving only a small night light on.
Later in the scene, as Mary sings the song, the camera moves indoors. The lights are fully on in the house for the living room, entrance, and stairs. Mrs. Stone is standing by the downstairs phone listening to Mary sing, while going through the mail. The camera returns to the porch showing Mary singing and we can see the lights are off (other than the night light) and there is no sign of Mrs. Stone.
After a little bit more time, the camera moves back inside again. The lights are all on and we see Mrs. Stone walking upstairs, with the mail, and listening to Mary sing out on the porch. As Mrs. Stone disappears up the stairs (for the second time), the camera switches to the porch and Mary continuing to sing. The lights are again off, other than the night light, yet they were on as Mrs. Stone was leaving to go up to the master bedroom.