Other mistake: Keira Knightley looks down at her phone, there is a beautiful female hand holding the phone with long slightly curved nail beds. This is not Keira's hand which is seen many other times times throughout the film. She has shorter nailbed and flat nails. (00:22:37 - 01:13:56)
Other mistake: Travers arrives in Los Angeles and is seen at the airport and the hotel a short time later with just a small suitcase and a smaller carry-on bag, yet she has far too many clothes-suits, dresses, skirts, sweaters, blouses, sleepwear, shoes, and other accessories-than could possibly fit in them. She is seen leaving L.A. with an additional suitcase, but the third one appears to be one that is just used for carrying the big Mickey Mouse stuffed toy she takes back to London.
Suggested correction: There's nothing saying that she had to have taken all those clothes with her. It's possible that she had more clothes sent on afterwards. Maybe the extra clothes belonged to the hotel/studio etc. Maybe they were rented. Who knows? Just because it's not explained, doesn't make it a mistake.