Other mistake: When the girls leave camp they wave good-bye to each other. If you look closely it is obvious that one of the girls (the one in the distance waving) is a double who does not look like Susan / Sharon at all.
Suggested correction: No one is waving in that scene. As a matter of fact, the one "in the distance" can't wave because both hands are holding suitcases. They kissed goodbye, not waved.
Other mistake: After the camping trip, in the kitchen, Maggie McKendrick remarks that the camping trip ended early. (It did so because of the blowout with Vicki.) Later, Maggie tells Mitch that she had made extra food for him and Susan for the next evening (done before they got home), because she and Sharon would be leaving in the morning. This is inconsistent.