(at around 12 mins) Some of the time that the Barber and Schultz are upside down, they are backwards. They actually switched seats and the Barber is now on the right, instead of the left where he properly belongs.
(at around 27 mins) When Hannah has tomatoes thrown at her by the soldiers, she has three prominent streaks of dirt on her right cheek as she cowers to protect herself. When she gets up after the attack, the dirt is missing from her cheek.
(at around 12 mins) When the Barber flies upside down in the aeroplane, he sits at the left, closest to the viewer. Schultz asks him for the time. Near his elbow, the G from the text "G 3824-R" is closest to his elbow. Later, when he gets his watch to answer the question, the plane seems to fly normally, but then the Barber sits at the right, where it is the R which is closest to his elbow.
(at around 53 mins) When Adenoid Hynkel climbs the curtains, his left leg is up/down between shots.
(at around 30 mins) When the Jewish Barber has just returned to the Ghetto and is cleaning his windows, his white overcoat changes from buttoned to unbuttoned throughout the fight scene.
(at around 30 mins) When the Jewish Barber cleans the word "Jew" off his shop window, a dotted line can be seen to mark where the W would be painted again for the next take.
(at around 11 mins) When the Barber and Schultz are flying upside down, the wire waving Schultz's scarf is visible.
(at around 29 mins) When the Jewish Barber first finds his shop full of webs, the shadow of the camera can be seen on his left shoulder.
(at around 5 mins) The machine rolling the bomb around in the beginning can be seen.
(at around 42 mins) When Hynkel opens the filing cabinet behind his desk to reveal and look into the full-length mirrors inside of it, studio lights can briefly be seen reflected in them.
(at around 35 mins) When the Barber is chased in the Ghetto streets by Stormtroopers, one California studio building can be seen in the upper right corner of the frame.
(at 37mins) When the inventor of the bullet proof uniform greets Hynkel, he salutes with his left arm while it should be his right arm.