When the dog pulls on Tom's pant leg trying to get him to throw the ball, it shows that he pulls apart a few of the buttons. In the next shot when it show's Tom's pants from a different angle, the pants are fully buttoned again.
When they are in the truck carrying the wrecked car, on the way to the pension, the exterior shots show the truck driving through a rural mountain landscape, but during the interior shots showing the three people talking a suburban environment including cars parked in driveways can be seen.
The castle/hotel is supposed to be located in France (in fact it is "Burg Taufers" close to Sand in Taufers, in South Tyrol, Italy). The Tyrolian Flag on the wall belongs to South Tyrol. Despite the fact that the cars have the correct French license tags, you see a local construction company's truck (Kiesunion) on the highway. Also the electrical sockets in the bedroom are Italian and not French. The uniforms of the firemen coming out of the castle after the fire are clearly not French (the helmets used by the firemen are former Wehrmacht helmets repainted in white and are commonly used by fire brigades in Germany, Austria and South Tyrol but not in France).
When Sarah is in Italy, in Piazza San Marco (with the pigeons), she's reading from a guidebook that says "Florence & Tuscany" - however, she's in Venice, which is a city in the region of Veneto, not Tuscany.
In Venice, Sarah is shown in a large rectangular room filled with paintings by Tintoretto (which she had earlier declared her desire to see) and then leaves and is accosted on the stairs by Peter. However, the room with the Tintorettos's is in the Scuola Grande di San Rocco, not in the Santa Maria della Salute Church, which is where she is shown leaving. They aren't even in the same neighborhood. (And La Salute is in the shape of an oval, and has no rectangular rooms)