Continuity mistake: When Filch is holding Mrs. Norris the cat's eyes are not red, but in all the other films they are.
Continuity mistake: Dobby's grave at the beginning of the movie has been moved further to the right of where it is was dug by Harry at the end of the Deathly Hallows Part 1.
Continuity mistake: While camping and searching for horcruxes, the size of the trio's tent changes from location to location. Harry is standing beside it while Ron and Hermione are skipping stones across a body of water, and the tent is fairly tall. Other times, it's very short like a pup tent and they must stoop to enter.
Continuity mistake: When Harry jumps on the dragon, his hair is wet and messed, then it changes to dry and brushed and in the next angle, for a brief moment, it's back to wet and messed.
Continuity mistake: When Voldemort and his followers return for the final battle with Hagrid carrying Harry, the remaining building structure has fires in each section. When Harry and Voldemort land there during their duel, the fires are gone.
Suggested correction: Obviously, the fire had plenty of time to die out.
Continuity mistake: After Voldemort disapparates while Snape is dying, Harry asks Hermione for a flask for Snape's tears. She pulls a vial out of her purse. However, she hadn't had a purse during the entire prior battle, then suddenly has one at this moment. Afterwards, she no longer has the purse in any other scene.
