In the first scene, Rico orders spaghetti and coffee for two. When the meal arrives, he cuts it up and eats it with a knife and fork; it doesn't look anything like spaghetti.
In the diner scene, Rico jumps from reading the newspaper to eating his spaghetti between shots.
When Rico and Massara are in the diner, the waiter brings them spaghetti and coffee then walks away. On the following shot, there is now a plate of bread between them that wasn't there before.
In the diner, Rico and another man are talking while Rico is reading a newspaper in a medium shot from the front. The waiter walks up with the food, and Rico folds the paper and puts it down on the counter as the waiter serves the food. There is a cut to a full shot from the end of the counter as the waiter walks away from Rico and towards the camera - Rico is clearly visible holding and reading the fully open newspaper that he set down. Then there is a cut back to the medium shot from the front, and Rico is eating with the paper folded and on the counter in the same location where he put it earlier.
In Big Boy's study, when he starts talking to Rico about Pete Montana, Rico has a cigar in his mouth. When the shot changes, the cigar is gone.
After Tony was killed, he received a big funeral possession; however, historically such a traditional big send-off would have been reserved for a major mob boss only; not a low-level hood.
Rico is hit by the bullet sufficiently to require bandaging by Scabby, but the overcoat he was wearing has no bullet hole in it, nor is there any trace of blood in the subsequent scene in Little Arnie's office.
When Rico is shot behind the billboard, the Thompson submachine gun used by the police detective has a blank-firing device attached.
When Rico leaves the newsstand heading toward the scene of his ambush, he's walking from left to right (as seen by the audience, the point of view referred to here throughout). Then there is a cut to the truck, with its concealed gunman, and it's heading toward him from the opposite direction. The truck's starting point, therefore, must have been in front of Rico, or to his right, but the trail of bullet holes created by the moving gun begins behind Rico, that is, to his left. In other words, the bullets striking the plate glass window behind Rico should have moved from right to left, not left to right, as they do in the movie.
Microphone shadow moves across Tony as he closes door just after his mother has left room.