Continuity mistake: The pillow behind Griphook constantly moves between shots while the Trio is talking to him at Shell Cottage.
Continuity mistake: During the epilogue, Hermione hugs her daughter Rose. In the first shot, Rose's left hand rests on her mother's back just below the shoulder. Cut to the following shot and the same hand is on Hermione's arm instead. (01:56:00)
Continuity mistake: After arriving in Hogsmeade, when Harry is talking to Aberforth Dumbledore, the table by the window has two chairs on one side of the table. A few minutes later, there's only one chair on that side, and the other chair is now at the end where there was previously none at all. (00:28:00)
Chosen answer: Hermione knows this is an unusual request and she and (and Harry) suspect the bank knows that Bellatrix's wand was captured by Harry Potter (at the end of Part 1). Showing the bank manager the real wand would prove that this is not Bellatrix. The bank and Voldemort's minions expected that Harry and the others might go to Gringotts searching for a Horcrux in the Lestrange's vault. They are setting a trap for Harry and his accomplices.
raywest ★
Incidentally, if I remember right, in the book Hermione actually does hand over Bellatrix's wand, not realizing the Gringotts goblins already know the wand is no longer in her possession, forcing Harry to cast a timely Imperius Curse to avoid the entire plan being exposed.