Continuity mistake: When Ana and Christian are having sex on the dining room table, she drops Christian's pants below his butt. Scene cuts and Christian's back is shown, with his pants above his butt. Then cuts back and they're below again. (00:54:40 - 00:56:50)
Continuity mistake: When Jack calls Ana from Mia's phone, he makes his demands and throws Mia's phone in the water. Then from the bank Ana calls Jack on a cell phone.
Continuity mistake: When Anna is lying on the concrete and you hear Christian say, "Anna, breathe," she disappears while cops are arresting Jack.
Answer: He was trying to make her understand how she made him feel whenever she broke a promise (usually about her safety) by punishing her and it became too much, too intense. She also felt like it was revenge instead of love.