When Tony throws a spittoon through the glass door of the First Ward Social Club, the pattern of shattered glass before he enters club is far different from that as he goes into the 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 Angelo collapses after answering Poppy's phone call, the arrangement of the telephone and handset changes between shots.
When Poppy visits Tony, she holds the flower, but Tony has it in the next shot.
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.
When Tony pushes and punches the man who refuses to obey Johnny Lovo in First Ward Social Club, it's seen that Tony actually punches the man's palm.
When Tony is driving to get away from the gangsters who are chasing and shooting at him, his car windows are being blown out. However, no fragments of glass are seen flying around in the car or landing on Tony's clothes.