Other mistake: When Whoopi first takes over the choir, she asks the sisters to stand according to their singing voices. She asks where the sopranos are, and several women on opposite corners of the grouping raise their hands. She asks them to all move over to the left group, but only one of the two women on the right side actually does so.
Other mistake: After Frank's first visit to Rachel's house he's in the car and in the last close-up shot of him when he's about to drive away, he puts the car into park.