In her first scene with Stefan and Kai Sabine features a (fake) golden septum piercing that is missing in her later scenes.
When Kai and Stefan talk to Kai's stepson in whose room, in one shot the door is open and in the next shot the door is closed. Following this, in the next take the door is open again.
At the beginning of the movie when he was talking to his step son, the door was half open and when the camera changed and got back on him, the door was closed then they changed the camera again and it was half open again.
When Stefan checks in for his flight to Dubai he does so at a Lufthansa first class / business class counter at Cologne airport. Lufthansa doesn't serve Dubai (DXB, DWC) from Cologne. Moreover, it would make more sense for Stefan to fly in and out of Frankfurt, since Cologne is much farther from Wuerzburg.