(at around 1h 13 mins) When Vicki is killed, her demise comes as Mrs. Slater's cane comes down upon her left eye socket, spurting blood as it impales. When Dr. Beck and Kathryn discover Vicki and Liz's bodies in the open grave at Park View Cemetery, Vicki only possesses her chest and back wounds, no eye damage.
(at around 41 mins) Diane locks the kitchen door and remains next to it. In the next shot, she's leaning against a counter. In addition, later, Katie runs out of the kitchen, without anyone unlocking the door.
(at around 44 mins) When Morgan is removing clothes from Mrs. Slater's closet, she ends up removing the same outfits a few different times.
When Kathryn flees into the second upstairs bathroom stall she discovers Jeanie's decapitated head in the toilet bowl and the blood from her murder all upon the tiles surrounding the bowl. Jeanie was murdered and decapitated in the third upstairs bathroom stall with her head come down to the toilet bowl within that stall.
(at around 18 mins) The stocking on Vicki's right leg is gone just before Mrs. Slater tears the hole in the water and then quickly reappears.
When Katharine gets the gun she puts the clip in but never puts a bullet in the chamber. This fits as when she tries to shoot nothing happens. But then after running upstairs she cocks it but still doesn't load it. It would click, but not fire, yet it does fire the next time she tries. Then she shoots three times and throws the gun away when it looked like there were many more bullets in the clip.
(at around 1h 21 mins) When Dr. Beck falls over the stair railing, the person falling is clearly a much younger stunt double.
(around 1 hour 26 mins) The first three shots of Eric wearing the clown costume in the attic with Katherine, it clearly shows Eric's actor without his wig. The next shot Eric's actor wears his wig underneath the clown hat.
When the girls force Mrs.Slater at gunpoint into the pool to retrieve her cane, she could not have had enough time to get it, come out of the pool, and attack the girls in the time allotted.
Kathryn goes into the third bathroom stall to hide. The locking knob is shown being unlocked from the outside. There is no outside lock on stall doors.
In the beginning of the movie, Dr. Beck appears older than Mrs. Slater when she loses her baby. Later on, Mrs. Slater is much older, but the doctor doesn't seem to be much, if any older than he was when shown in the opening scene.