When Amy is stabbed she gets up out of bed. In one shot there is a thick spot of blood on the right shoulder of her night shirt as she gets out of bed. Then, as she stands next to her bed for a few seconds, the blood on her right shoulder is now light and smeary and not thick as was already shown. When she gets into the bathroom there is now no blood on her shoulder.
Amy fakes out Winter and stabs the knife into the table next to the bed, the table holding The Puzzle Box. At first the blade is turned away from Amy, the next shot of the knife shows the blade is turned toward Amy. Then, as she grabs The Puzzle Box off of the table, the knife blade is turned away from Amy.
After Winter and all the deaders die, and Amy facing Pinhead, stabs herself, you can see blood drooling from her mouth, in the next shot she is crashing down, and her face is clean, the next shot of her shows that she has bloodstains on the left edge of her mouth.
In the scene where Amy grabs the envelope and the box from the "dead" woman in the bathroom, she takes the box from the woman's left hand and puts it in her bag. When the woman "awakens" you see Amy jump away. The scene then cuts to the woman in the bathroom and she is still holding the box in her left hand after it was supposedly removed.
When Amy is talking to Marla's landlord outside Marla's door, the landlord's cigar is burned almost completely down. After the door is opened and Amy enters, the landlord can be seen outside with a much longer cigar.
When Amy gets off the train, a clock in the background reads 17:46. A few seconds later, when she stares at the guy in the long coat, the clock behind him reads 2:26. Two shots later, the time jumps to 2:55! After some time has passed, the cops arrive, and Amy runs down the stairs after the guy. Now a clock in the background reads 2:53.
Although the paper is based in London, the money in the envelope that Charles gives to Amy is American currency. Likewise, the bribe that Amy gives to the landlord in Romania is also in American currency.
When Amy unlocks the gate she only unlocks the lock without removing the lock itself and gets right through with a push even though we can see the chains wrapped around it multiple times. After she walks through, we can see that there are now no chains or lock on the gate at all.