Plot hole: In the end of the film it is heard the police want to exhume the body of Charles Lee Ray from his grave site in New Jersey. Now when Chucky and the crew get to the grave site they find and kill a coroner who is digging up the body. He is the only one there at 1am, by himself, a lonely coroner without any police officers, after all this is a police investigation and I doubt the cops would have him there alone. Then right at the end the Detective who is hunting them arrives. Now he is a cop from Lockport, about six states away. A. Why did he drive all that way to see the body? B. A cop from all the way down there shows up but no new Jersey cops are at the scene?
Plot hole: When Tiffany locks Chucky in the wooden cage, (The "Nursery" she calls it) you can see her lock the top. The problem is that the lock is put on in such a way that it would not actually keep Chucky in the cage. It is on the top of the cage, but doesn't connect with the cage at any other part. It simply wouldn't work.
Plot hole: In this film Chucky says they need the heart of dumbbells to transfer their souls into human body. If he knew this why did he even attempt it in the first 3 movies? And he never uses it in the next 3 movies, including "Cult of Chucky," where he is successful at the transfer. (Side Note: The series writer has admitted that this was a ret-con added to the film in order to justify the road-trip. So, while still a mistake, it was purposely done).