Carson tells Alfred that a footman should not be over 6 feet 1 inch tall. Although Matt Milne who plays Alfred is 6 feet 5 inches tall, William the footman was played by 6 foot 3 inch tall Thomas Howes.
When Sophie and Tom arrive and go in, Alfred is told to get their luggage and take it in. As the scene ends, Alfred is seen going inside empty handed.
When Robert is telling Cora he lost her money, she has her hair on her chest with a ribbon while you see her face, but on her back without the ribbon while you see his face.
The automobile Cora's mother arrived in is the Cadillac V-63. The scene is set in 1920, and the model wasn't introduced until 1923.