In the bowling alley scene, Carolyn bowls a ball toward a set of only a few pins. In the next cutaway shot, all of the pins are there as the ball rolls through them.
The model of the car following Jerry Bartowski in one of the final scenes varies. In some shots it's a 1969 Chevy Impala; in others it's a 1969 Chevelle.
When Zeke is on the bridge over the highway talking to the union guys, a 'cars produced' counter is visible in the background. The count jumps back and forth, and skips hundreds of cars.
When Zeke is called into the office after mouthing off to the shop foreman, the three other characters take a seat at the table but Zeke is standing. Behind him, the office door is partially open. In the next shot, the door is now closed.
Whenever the actors use air powered tools, they just pretend. The tools just spin in mid air.
Jerry mentions that his car needs a "gas" pump, which is technically what it is, but people familiar with cars and certainly people who build cars for a living would use the more common term "fuel pump."
REVEALING MISTAKE: When Smokey is getting killed in the sprayer booth, he tries all means of escape except the most obvious: getting in the car that was being painted and driving through the doors, since the car had to have the key in it.
When Jerry, Zeke and Smoky are casing the union hall, Jerry asks "Who is in the Buick?" The car he is looking at is an Oldsmobile.