On the laser machine, the word "RECEIVE" is spelled "RECIEVE".
During the demonstration of the ultrasonic projector, the wine goblet would not have danced the way it did, as the resonant frequency for the goblet would be in the audible range, not the ultrasonic range.
When the purple bruise first appears on Halder's temple, supposedly from a ruptured artery, you can clearly see the purple dye on his hair.
When Jim is listening to the tape, the selector on the player is in the rewind position.