When Frank Bono attacks Ralph in Ralph's apartment, his gloves disappear and reappear several times during the struggle.
As Frank pleads with Lori not to kick him out, the state of his necktie alternates between loose and tight several times.
When Frank Bono is walking down the sidewalk ready to enter the building in which Troiano's girlfriend lives, the street and sidewalk are dry. Just as he turns to go up to the entry of the building, the camera view switches to a different angle, and now the street behind Frank is wet from rain.
The "silencer" (or suppressor) that Frankie Bono attaches to his revolver could not have worked due to the gap between the cylinder and barrel of the gun. They are only effective on semi-automatic or automatic weapons, except for one special revolver (when the film was made), the Nagant M1895. The Nagant had a 7-round cylinder, but Frankie's gun was a 6-shooter. This is a very common mistake in films.
Although the silencer provided for the gun might be attachable, it would have been useless for suppressing most of the revolver's firing noise. With a revolver, flash and noise emit from the front of the cylinder, which has no gas seal. A silencer on the front interferes with gas escaping from the end of the barrel, so it would likely increase the noise at the cylinder front. At the time the film was made, only one revolver design was available that mechanically pressed the cylinder forward to seal against gas emission, and could thus be noise suppressed. That gun was the Russian-made Nagant M1895, which used exotic 7.62×38mm ammunition. Frankie's gun was shown clearly to have a 6-round cylinder, so it could not have been the Nagant, which has a 7-round cylinder. Also, such an exotic weapon would not be available for Frankie's cheap purchase from Big Ralph.
At the beginning, Frank is depicted as arriving in New York City. However, the train pulls into Newark's Penn Station in New Jersey and he gets off. Then he is shown going through the main hall of Penn Station in Manhattan and getting into a taxi there.
Frank is tailing Troiano on the Triborough Bridge as he takes a right to exit to get on the section to Manhattan but the action then shows they are now on the upper level of the Queensboro bridge entering Manhattan several miles south.