When Reeves is at Ripley's house, he prepares a tray with his breakfast and walks from the kitchen into the library. In the shot before he goes through the interleading door, the only bottle on his tray is his beer. When he sits down in the library he suddenly has a bottle of HP sauce on his tray as well.
When Ripley and Trevanny leave the train station, they are supposed to have arrived in Düsseldorf. The approaching police cars have license plates with a 'D' designating them to be in Düsseldorf. However, behind the police cars, the letters "City Carré Passage" can be seen on a building. There is no shopping area with this name in Düsseldorf. They are still in Berlin, at the main train station.
When the train which Trevanny takes to Duesseldorf leaves Berlin, a historic building can be seen through the windows. This is the "Theater des Westens" which is located just north of the tracks and west to Zoo Station. So the train is traveling east while to reach its destination it would have to go in the opposite direction.
As Tom Ripley leaves the Trevannys' house after the home invasion, he tells Sarah to call the police and report it as a burglary gone wrong. However, he takes the gun he used to kill the two 'burglars', and which will make it difficult for Sarah to explain how the two men were killed with a gun that is no longer there.