Lisa is (obviously) not wearing panties when bowling. Panties are visible during the rape scene.
After BBK's head is blown off, he drops the switchblade. Later, Lisa takes the switchblade out of his hand, even though he dropped it earlier.
More blood on Steve's smashed face after Steve dies.
Sarah loses her tights in the final blood bath but regains them when she exits the building.
Egerton gets decapitated when his head gets blown up with the shotgun; his head then hangs off the neck stump. His head should've exploded rather than be hanging.
A.J. gets killed when his face is waxed off. The aftermath of his face shows that it has been melted off, even the skull; it would be impossible to have a whole face or the skull for that matter, melted off / dissolved in a bowling ball polisher. Therefore, he could've at least had third or fourth degree burns all over his face and his skull would still be intact.
Lisa grabs Patrick by his throat with her right hand. In another shot during the same scene, she grabs his crotch with the same hand. In the next shot, showing Patrick from the neck up again, her right hand is still around his neck.
When Steve getting bludgeoned to death in subsequent shots, his face is clearly a dummy.
In a majority of the close-ups of all the dead bodies, you can see the actors breathing.
When A.J.'s face is first shown after briefly getting forced into an automatic bowling ball polisher, it's clearly that of a dummy.
After Egerton gets his head blown off with a shotgun, blood sprays out of his neck stump yet none shower on Jamie.
This movie is supposed to take place in the 1980's but in the rape scene we can see "Daytona USA". This Arcade was released in 1993.
This film is set in the 1980s, yet all the Pepsi vending machines feature a more modern logo.