When the boyfriend shoots and hits the door frame during the first 415 call, the point of impact is easily seen due to the wood splintering. When Reed and Malloy leave the apartment, the point of impact is covered with black paint so fresh damage isn't easy to see.
Sgt MacDonald is not in his usual car - a station wagon. He's driving a traditional patrol car.
At the first 415 call, Wells rushes at the door, with Sanchez close behind him. In the next shot, Sanchez appears from around the corner of the exterior hallway.
When Malloy and Reed go to the first call (the drunken man with a gun), the exterior of the apartment building is seen with its white stone exterior. When they are later on patrol, they respond to a call about a man with a six year old, and they pull up with the camera in the back seat of the car. As the car stops, one can see the same apartment building through the car's front window, showing they shot both scenes at the same location.
When Wells gets shot, Sanchez, Wells' partner, racks a round and fires at the suspect. He racks another round but no empty round is seen leaving the shotgun. He then fires another round without racking another round.
When the gunman who shot Wells throws the gun out, he appears to yell something, but no sound is heard.
In Log 152: A Dead Cop Can't Help Anyone (1969), Wells' wife is named Betty, but in the The Late Baby (1972), Wells refers to her as Eileen.