The position of the gray pantyhose on the floor keeps changing.
As Dr. Feinstone chases Sarah around the dentistry, the position of Sarah's pin-on bib which she wears, continuously changes.
(at around 21 mins) Jody's lei vanishes/appears repeatedly as his mother carries him away.
(at around 31 mins) When Dr. Feinstone was getting ready to do a filling on April, he placed a saliva ejector (small suction) in her mouth. It was there for several shots, then suddenly vanished.
(at around 58 mins) Jessica's ponytail when she confronts Dr. Feinstone in the doorway.
(at around 25 mins) There is a comment as to Dr. Feinstone referring to the wrong tooth on April. #31 is the Lower Right 2nd molar in the Universal Numbering System. In the FDI system #31 would be the lower left incisor. In 1996 the Universal Sytem was the one in more common use.
(at around 29 mins) While starting to do a filling on April, Dr. Feinstone started up the handpiece (drill). The sound it made was that of a high speed handpiece, yet what he had in his hand was a slow speed handpiece.
The light equipment can clearly be seen in Dr. Gibbs glasses a few times.
(at around 1h 9 mins) When Detective Gibbs arrives the bedroom of Dr. Feinstone and Brooke and open this door you see a leg of a light stand.
(at around 14 mins) When the dog attacks Dr. Feinstone you see in the shadow the cameraman and a other crew member.
(at around 25 mins) When examining April's radiographs, Dr. Feinstone points out to Karen "There's a shadow here on number 31", which is the lower left central incisor tooth, but then says to April "You have a cavity on one of your lower right molars".
When Dr. Feinstone is at the dental school, and sees the apparitions of his victims, Karen asks him, "Why did you kill me, John?" The doctors first name is Alan, not John.