At approximately 34:35 into the film, the time on the clock in the room suddenly changes from just after 2 o'clock to 3 o'clock. Then at approximately 37:00 it moves back to 2:05 and then to 2:09 as Dorian continues to play the piano.
When Dorian confronts Allen Campbell with the blackmail letter in his drawing room, Allen sits at the round table, which has only the cat statue and the letter on it. In the next shot there is a writing implement on the table as well.
An American version of a Brit Railway Station - Toward the end of the movie Dorian (Hatfield) and Henry Wotton (Sanders) arrive at Selby Station, Yorkshire, England. The train pulls into the "stationhouse" platform which is to the most right-hand side coming UP from London. That would be correct for an American RR Station but the absolute wrong side for Britain; the Brits both drive on the left-hand side of the road and also run their trains that way.