When "Simon" is about to enter his hotel room, the hinges on the door show that it would swing out into the hallway yet when he opens the door, it swings into his room.
After Simon witnesses the murder of Fillipo, he jumps on the back of the murderer. He then falls to his knees on the stone walkway. The camera cuts to a close-up of Simon and instead of being on the walkway, he is mostly concealed in the shrubs alongside the walkway, which he then leaps out of.
(At about 45:00) Though supposedly in Geneva (Switzerland), when Simon looks at a train schedule, it is in English, for service between Chicago and Montreal.
Obvious use of stunt double when "Fillipino Ravenna" is attacked as that the character is balding yet the double has a full head of hair.