Other mistake: When Harry, Ron and Hermione rush to Hagrid after the end of the year exams, and Harry is saying something that ends with, "Why didn't I see it before?", Hermione is mouthing part of that line. [Emma Watson did admit she learned Dan and Rupert's lines as well as her own and found herself accidentally mouthing them.] (01:50:40)
Other mistake: While Hermione and Ron watch, cloaked Harry starts up with Malfoy and his two friends as they all stand in the snow. Most noticeable in the wide shot, when Harry spins the Slytherin boy, although the boy's feet visibly disturb the snow, Harry's feet do not make a mark - no footprints whatsoever. (01:02:30)
Other mistake: In quite a few shots during the film, it is much too obvious that there are no lenses in Harry's glasses, whereas in previous and following shots the glasses have lenses. A couple of instances are: when Harry drinks the Felix Felicis and when Harry kneels beside Dumbledore, at the foot of the Astronomy Tower.
Other mistake: In both the books and the movies, Harry's Invisibility Cloak can always be seen until it is worn. In Diagon Alley, just before the Gringott's break-in, Ron pulls out the cloak to cover Harry and Griphook, but it turns invisible before he puts it on them. Ron merely mimes the motion of covering them.
Other mistake: While downstairs Vernon hears Hedwig's squawks, as well as Dobby and Harry's exchange in the bedroom upstairs, distracting enough for them all, including the Masons, to take note. The noise upstairs illicits a reaction from everyone, which Vernon explains is a noisy cat. Yet when Harry very noisily chases Dobby down the steps, Dobby slams into the wall and Harry lands with a loud thud (not remotely 'catlike'), Vernon, who stands on the other side of the shared wall, pleasantly continues his story to his rapt guests, who are also not distracted by the noise. To suggest that such loud noises coming from the hallway right beside them would not draw any reaction from anyone, Vernon and the Masons included, is preposterous. (00:06:45)
Other mistake: When Newt gives Jacob a suitcase full of eggs, he bumps into him, apparently swapping suitcases. If you watch carefully, the suitcases don't actually switch.
Other mistake: In the Forbidden Forest, after Grawp has put Hermione down after grabbing her, he turns round and bends down to pick something up. When the shot turns to Ron, Hermione and Harry they are still looking up at Grawp even though he's bending down. Their position doesn't move. Ron even looks Grawp up and down, even though he's still bent over with his back to the students. (01:27:10)
Other mistake: At the very end, the Durmstrang ship is leaving, it's away from the 'bank', firing its cannon. And then we see the Beauxbatons girls leaving Hogwarts... Followed by Durmstrang students whose boat has already left. (02:22:00)
Other mistake: Harry pulls a knife out of Dobby's chest, but before that, we can see there's no knife.
Suggested correction: Yes there is, Dobby is holding on to it as he falls into Harry's hands. Its not totally obvious, but the CGI people definitely put it in.