After the demon falls on Hannah from the balcony he pukes slime all over her but in the next scene her clothes are clean.
When the helicopter crashes against the floor of the cinema, there are no dead pilots in it. But in the next shot their bodies appear.
Just after the young boy shoots demonic Cheryl, the jeep begins to drive away into the dawn. One shot later, it is pitch dark -- no morning light is apparent.
When Cheryl is sitting in the subway car she is holding her piano book Mikrokosmos right-side up. As she steps out of the subway car onto the platform at Heidelberger Platz, we can see multiple alternating shots of her holding the book upside down as well as right-side up.
In the scene where George and Cheryl have climbed out onto the roof of the cinema, a shot across the city skyline shows that there is a crescent moon. In the final shot of the film, a full moon is visible in the sky on the right hand side of the screen (it's the same night).
When the movie goers first enter the movie theater, there seems to be no pay phones around. Common at the time, there should have been at least one but there isn't any. The movie goers also don't to even attempt to use a landline telephone, to try and call the police. This makes no sense, it may not have worked, but still not one of them even attempts to use the phone.
Moviegoers find out that they can't leave the cinema - there is no way out. But when Metropol is shown from outdoors, we can see lightened rooms through the windows. Were characters too dumb to jump out from the windows or to take down using the rope?
At the end scene during the motorcycle chase, Nina's demonic character is not wearing any demonic makeup.
When the black guy as demon grabs the man and slams him onto the chairs, in the background you can see the man being assaulted by a demon, but he doesn't seem bothered with it, clearly not acting it to the end.
The blades of the helicopter couldn't cut the demon's stomach because propeller was disposited too high, as we could see in the previous shots.
A man with a mask blinks while being dead (his head is impaled).
When the main character is riding the motorcycle, he runs over a man laying on the ground. He clearly does not move out of the way, showing that it's a dummy doubling for the actor.
When the girl is running from the masked man through the supposedly empty train station, two men are seen smoking behind a pillar.
It seems unlikely that none of the moviegoers ever questioned the redheaded lady working for the theater as usher.
Demonic Carmen was never seen in the film again after killing Frank. Every body was trapped inside, and There were lots more moviegoers to slaughter. Where did demonic Carmen go? She was probably killed off screen, as the film has a high level of gore even for the time and her death was likely cut to try and maintain a theatrical rating, just because you don't see it on screen doesn't mean it didn't happen, it just isn't explained.