When Carter leaves the Dysens' house for the meat packing plant, he doesn't wear a hat and drives over in a borrowed car (i.e., his hat wouldn't be in it). He's then seen at the plant with a hat on.
The car Mike Carter steals from the two detectives is a 1939 Buick. As he drives through the city streets it becomes a 1935 Buick. When he abandons the car it is again a 1939 Buick.
Mike Carter (Lawrence Tierney ) parks a station wagon outside an amusement arcade the driver of the car behind finding himself boxed in uses his car to push the station wagon forward and does so easily that it's obvious that the handbrake isn't on. The front bumper becomes level with a fire hydrant. There's a shot of Mike in the arcade Thern a shot of a police officer looking at the car but now the front wheel is level with the hydrant.
At 19 min when Mike enters Doris' apartment part of his tie is twisted and sticking out of his suit with the label showing; in the next immediate shot it is neatly tucked into his suit.
After Mike quits the force, he and Doris attend a baseball game which is tied in the bottom of the 9th inning, with two outs against the home team. The first pitch shown is a strike that the batter swings at and misses while a player on first base steals second base. The second pitch shown becomes a double into left field, scoring the runner from second base. At this point, the game should be over since the home team broke the tie in the bottom of the 9th. Nevertheless, the game is shown as continuing with the first batter now on second base. The next pitch shown becomes a single into right field, scoring the player who was on second. The home team now has scored twice in the bottom of 9th, yet the game continues further, with the next batter hitting a grounder to the shortstop, who gets a force-out at second. Finally, the game is over and Mike and Doris seem suddenly upset that their team (the visitors) have lost on that last out when in fact the game was lost two batters earlier. Even worse, a last shot of the scoreboard shows only one run for the bottom of the 9th instead of two.
The inside of the trailer Mike enters (a studio set) is much larger that it appears from the outside.
Mike Carter jumps out of a car just before a train hits it. The front of the engine should read Santa Fe, but the image was reversed and says " EF ATNAS"
When Carter drives up to Dysens' house, the handbrake can be heard long before the car actually stops.
Since Doris, in the penultimate scene, is crawling on hands and knees through sawdust, it would have been blatantly obvious to Freddie where she was hiding.
A moving reflection of the boom microphone is briefly visible in the upper right corner of the mirror after Connie Fenton and Mrs. Dysen leave the room to go to bed (at 14 min 49 sec).
Freddie asks Doris (Priscilla Lane) who she is when he confronts her in the meatpacking plant towards the end of the movie. But she was actually with Mike when Freddie offers Mike the bodyguard job at the ballpark at the beginning of the movie...seated right next to Mike. Freddie could have not noticed her since they weren't properly introduced but c'mon...it's Priscilla Lane.