Sandra's hair is longer during the cemetery scene.
When she and Carol are dancing, Sandra raises her arms and her midriff shows. Later, when she removes her top, a camisole has appeared.
When Mr. Wallis is teaching Sandra to aspirate the corpse he pushes the trocar straight in. In reality the trocar would be inserted at an angle and then be inserted in a complete circle to insure as much fluid as possible is removed. Also the body would be bathed after embalming.
When Mr. Wallis is teaching Sandra to embalm, he is working on the left side while explaining the jugular/carotid injection method. In reality one point embalming is done on the right side.
As Sandra touches the folded hands of the male corpse in the casket at the Wallis Funeral Home you can see the "corpse" breathing; his suit jacket is moving up and down in a breathing motion.