When Esme and Carlisle arrive with their last witness Alistair, Edward informs Carlisle that 18 vampires have arrived, right after this scene Bella says in her voice over: "We opened our home to eighteen vampires." This is not correct because after Alistair arrived it should have been 19.
At the beginning of the movie, Edward's hair covers the mole on the right side of his neck. During the meadow scene, his hair has been cut short and you can see the mole. During Alice's vision of the future, Edward's hair is a bit longer and covers it again. His hair isn't supposed to grow.
When Bella is in the cottage re-reading Alice's note, she flips it over to show the title page of Merchant of Venice. There are no smudges on it then but when she goes to the bookcase to pull down the book, she opens it to the front and puts the title page in place and now there are 2 distinct dark fingerprint smudges on the page.
When Bella and Edward are lying together on the floor with the pillows and talking, she's on her side with her arm bent to hold her head up. Then she puts it above Edward's head when he mentions not being able to be around Emmett and Rosalie when they were first together. In the next shot, her arm is bent again.
In the last scene, Edward & Bella are in a field of beautiful, purple flowers. When Bella reaches around to kiss Edward & puts her hand on the back of his neck/head, her wedding ring is on that hand, which is her right...not her left, which is the hand she put it on when they were engaged & when they were married.
The biggest crime is if vampires reveal themselves to humans. While reading Edward's mind, Aro should have known that Bella's father knows partially about vampires as he has met Renesme too. This would have been reason enough to kill the Cullens.