When Michael has left doctor Moray's office, we see the cops who are starting their car just around the corner. As they round the corner, Michael's Porsche is still parked. In the next shot, the Porsche is suddenly gone.
When we first see David and another employee, they are checking out what happens in the gym through the security cameras in real time. After they have increased the bike resistance, they see Freddie taking over a bench from the blonde bodybuilder. This particular footage couldn't have been on the monitor, as it happened before.
When girl is impaled, the position of the exit wound doesn't match the position where the spike enters.
This film was written and produced in the mid-80s and by all appearances is meant to be taking place in the present day of that time. However, a party is advertised as happening on Saturday, February 2, which could only be an actual date in either 1980 or 1991, but in no year in between.
Whenever Catherine is seen burning, whether in the flashbacks or at the end of the movie, it's obviously a person in a fire suit.
Impalement wound is fake, obvious by the use of gore make-up which makes the flesh look really fake.
When Priscilla combusts, a doll is obviously replacing the actress in the frame just before the combustion happens.
The title of the soundtrack song "Killer Groove" is misspelled in the credits as "Killer Grove."
Actress Shari Shattuck's first name is misspelled in the closing credits.
When Laura breaks the glass with her hand, it would have cut her hand, but that doesn't happen.
One man jumps through the window and one is thrown through it, but they don't get cut by the glass.
Early in the film, when the lady is dancing in the gym, a woman in workout gear is seen in a mirror standing against the wall. Its not apparent if this is a crew member or the actresses' body double.
After Michael confronts Tom about sabotaging the club, they all step outside. The boom mic is visible on the left side, around the corner.