When the Baron is stealing Grusinskaya's pearls from her trunk, they clearly are a very long strand of large pearls. Later, when he pulls them out of his pocket to hand back to her, the pearls are small and on a shorter strand.
As Grusinskaya is on the phone (while the Baron is watching), she holds the receiver with different hands between shots.
After the Baron asks Flaemmchen for a date, he moves from behind her left shoulder to behind her right shoulder twice. Also, the Baron's cigarette seems to disappear without any indication he put it out.
Room numbers on doors change style occasionally. For example, sometimes there is a crossbar on a 7, sometimes not.
(at around 49 mins) When Grusinskaya picks up a phone to ring the Baron, she is leaning on a couch. In the next shot, she is standing with the phone in her hands.
When Grusinskaya returns from her second performance, she and her entourage board the left elevator, and the porters carrying her flowers board the right. When they come off the elevator, the porters and flowers are on the same elevator as Grusinskaya.
When Mr. Kringelein drunkenly slams his door shut, the wall visibly shakes.
The first time the Dancer walks out of her room, her shadow moves according to an obvious moving light, instead the static ones on the ceiling that supposedly are the only ones there.
Although correctly signed with license plates starting with an "I" for Berlin, all the cars are right-hand steered. In Germany they drive on the right (and ever did so), so the steering wheels should be on the left.
Grusinskaya's car arrives at night to take her to her performance. She and her entourage get in the car, and the car drives off without the car ever having its headlights on.