The slip-up occurs when Harrison Ford is talking to his girlfriend in the bedroom. She's sitting on the bed and he's about to walk out the door. The scene clips to him as he's standing in the doorway. If you look down on his jacket, it's buttoned. The scene then clips over to his girlfriend sitting on the bed. When it clips back to him his jacket is unbuttoned. The scene clips too quick for him to have time to unbutton it.