When Tony throws a spittoon through the glass door of the First Ward Social Club, pattern of shattered glass before he enters club is far different from that as he goes into room.
When the Northside guys throw a body out of the car, it lands face down, but when Tony and the others look at the body, it is face up.
When Poppy visits Tony, she holds the flower, but Tony has it in the next shot.
When Angelo collapses after answering Poppy's phone call, the arrangement of the telephone and handset changes between shots.
In the alternate ending, Tony is sentenced to hang December 10, 1931. The method of execution in Illinois in 1931 was electrocution. The last judicial hanging in Illinois occurred in 1928.
The scene Tony pushes and punches the man who refuses to obey Johnny Lovo in First Ward Social Club, it's clearly seen that Tony actually punches the man's palm.
When Louis is shot in a telephone booth instead of being slumped down, as would be expected, he's stretched out.
When Tony is driving to get away from the gangsters that are shooting at him while in a car chasing him, Tony's car windows are being blown out. However, no fragments of glass are seen flying around in the car or landing on Tony's clothes.