Revealing mistake: When Nica goes to investigate the screams in the first part of the movie, as she opens and closes the door she appears to be moving in a way that implies she is standing and not sitting in her wheelchair, this completely contradicts her being a paraplegic.
Plot hole: When Chucky is decapitated, no blood comes out. He still has the scars from Bride/Seed of Chucky so that means he's still in the same doll's body. The longer he remains inside the doll the more human he becomes, so he should definitely bleed by this point in time.
The production attempted to keep the cameo performances of Jennifer Tilly and Alex Vincent secret. They were unlisted in the cast and promotional material for the film. However, after early screenings of the film, their cameos were leaked online.