Other mistake: In "The Heart of the Truest Believer", Rumplestiltskin has his shadow removed from his body, and therefore should not cast a shadow. But in Neverland, his character frequently casts a shadow, especially in scenes with campfires.
Going Home - S3-E11
Other mistake: In the October 2011 flashback, when Mary Margaret gives Henry the storybook for the first time, he opens it to show Pinocchio and Geppetto in an illustration. However, according to 1-20 "The Stranger", Pinocchio's story was not added to the storybook until later after August came to Storybrooke, several months later. This is confirmed in 4-13 "Unforgiven", where Regina and Henry look at the exact same picture, and notice that the paper is different than the rest of the book, because this particular story was added by August. (00:17:00)
Chosen answer: Even if one can see the future, it can be somewhat vague and left open to interpretation.
raywest ★
He can sees the future all jumbled up. It is like a puzzle, it is hard to put together, but even when he does put it together it is not set in stone the future can change.