When Merida and Belle are at the Witch's cabin, Amy Manson rather visibly adjusts her wig,
The close up slow motion shot of Merida's arrow flying through the air shows the arrow flying perfectly straight, which is wrong because arrows wobble and bend from side to side as they fly.
The Yiddish word 'Nosh' is used by Zelena, a character brought in from a past fantasy realm who has not been exposed to the modern world outside of Storybrooke, in conversation with Emma in reference to the treats Emma brings for Zelena.
When Merida turns into a bear, her clothes shouldn't change with her, like in Brave, yet when Gold turns her back into a human, she has her clothes on when she should really be naked.