While Fowler is in his office, his round lamp on his desk is on when we are looking at him, off at a close up, then on again from a view behind him.
The plans for the Italian Consulate said "STAILWELL".
Unlike what's shown, Italian (or any other) consulate employees don't take citizens of the host country to the basement and don't beat them up to extract information. In accordance with the Vienna convention on consular relations, it's considered impolite to do so.
When Fowler's associate frisks Caffrey in the garage for bugs, he doesn't check his hat. Rookie mistake.