Visible crew/equipment: When Susan enters the building's stairwell, in the overhead shot you can see the reflection of the crew or equipment on the banister. It can't be Susan's reflection because she is relatively still, yet the reflection is moving and it is above where she could cast a reflection.
The Grudge (2004)
1 visible crew/equipment mistake
Directed by: Takashi Shimizu
Starring: Bill Pullman, Sarah Michelle Gellar, Clea DuVall, Jason Behr, William Mapother
Continuity mistake: When Karen goes into the cupboard upstairs, prior to meeting Toshio, she picks up a book. In one shot she picks it up by the page side, then when it cuts she is holding the spine side. (00:17:40)
Trivia: The Saeki family, the ghost family that haunts and terrorizes everyone who enter their home, are no strangers to the Grudge franchise. They played the same characters in the movie Ju-On, the Japanese version of The Grudge.
Answer: I don't think she actually went back into the past, I think it was just the house showing her what happened, or at least a type of visual echo of what happened. After all, some pretty strange stuff was happening in that house.
Mad Ade