At Maitland's home, when Axel takes a bullet in his right arm, Maitland emerges from behind the wall with a .44 magnum revolver. A gun of that caliber fired from that close would have most likely produced multiple fatal wounds.
After Axel goes through his racial tirade at the Beverly Palms Hotel, the blonde clerk looks down at the computer when the manager tells Axel how much the room will cost. In the next shot, she and the manager are looking straight at Axel, anticipating another racial outburst. In the shot after that, she is looking up from the computer at Axel.
When Axel throws Maitland's head goon over the salad bar at the club, the food on his face changes throughout the scene. He starts with a strawberry on his face, then it disappears and lettuce appears. The amount of dressing varies.
During the first car chase, Rosewood makes a sharp turn at an intersection, and the flashing red light falls off the roof. In the next shot, it's back on the roof again. The same shot is used in the second car chase, as they race to Maitland's house.
When Axel is thrown through the front window of Maitland's office building he is in the sun. When the police pull up, he is in the shade. As the scene goes back and forth between the two angles, Axel goes from being in the sun to the shade, then back to the sun.
In the shootout near the end, when the three of them jump over the wall at the same time, a shotgun is soon on the ground, and all of them shoot over the wall with pistols. The next time they shoot, Taggert has the shotgun in his hands instead of a pistol.
When Axel and Jenny first visit the warehouse, they see the crate being delivered and opened. Once the bonds have been removed, the top is replaced and four nails are sticking out, one at each corner. The shot cuts back to Axel briefly. When it returns to the crate the nails are gone. Not enough time has passed for them to have been knocked in.
When the cigarette deal gets broken up, three different models of police cars are involved in the first 20 seconds. They may have had rapid support, but the car that backs out of the alley changes completely once it's fully out.
When Axel asks Serge about the price of the table sculpture, Serge's hands are by his side. In the next shot of Serge, his hand is by his face. When the camera cuts back to Axel, Serge's hand is at his side again.
After the shootout at Maitland's mansion, Axel is seen from behind. He is wounded in his right arm, and has been using his left hand to shoot, yet his 9mm automatic is tucked into his belt in the back with the handle towards his right hand.
When Axel drives through Beverly Hills, the blonde woman in the car next to him raises her sunglasses on her forehead to look at him. When the shot cuts back to her, her sunglasses are in her hand as she puts them back on.
The tractor trailer slams into the fruit truck, which slides into a parked green Chevy Impala. Before the collision, the Chevy appears to have camera equipment under its front and rear bumpers, concealed by either black cloth or tarp. The rear camera's location becomes obvious in a slow-motion shot of the fruit truck sliding.
When Axel returns to his apartment to find Mikey waiting for him, he parks on a grade steep enough to cause his car to roll backwards. No hill in Detroit is that steep. In 1984, Detroit police were required to live within city limits.
Maitland's German bonds are incorrectly labeled "10,000 Mark". The official name for West German currency was "Deutsche Mark." East Germany used "Mark", but bonds did not exist there. In German the comma functions like an American or British decimal point, so the bonds were worth 10 marks.
Police drug dogs would not be fooled by cocaine shipped in coffee grounds. They would smell the drugs and the coffee at the same time. Even a few specks of powder on the outside of the crate would alert the dog.
The Detroit Police car that crashes into the Beetle during the truck chase has the license plate EAU535, with registration tabs. In Michigan,the third letter of a police car license plate is a small x, indicating a city or state municipal vehicle, with no registration tabs.
When Foley leaves Matlin's house to follow him and stops at the light, he loses the cops tailing him by waiting for the light to turn red before going through the intersection. A shot from the cross street showing Foley driving through barely missing cars shows that road with a red light. It should be green.
When Jenny Summers is being put into the Black Mercedes, the California license plate "6PHF248" is shown. The leading number 6 was not one of California's license plate assigned number schemes during the 1980s.
When Axel Foley checks into the Beverly Wilshire Hotel, he is given a room without being required to show any ID or provide a valid credit card. At the end of the movie, when Detective Taggart pays for Foley's stay, there is no cancellation of the prior credit arrangements made to secure the room.
While Rosewood and Taggart wait on Foley to come back to the hotel, Taggart drinks coffee from Dunkin' Donuts. In 1984, Dunkin' Donuts had several dozen California locations. They were phased out in the 1990s.
During the shootout when Axel, Taggart, and Rosewood are trying to get to Victor, all three fire at once. As Axel fires, his gun's slide goes back, indicating he has run out of ammunition. In the next shot, all 3 are firing again. Only afterward is Axel shown reloading.