Charlie must have a super power of fast healing. He got a scratch early in the movie that was attributed to a 'shaving cut'. However the cut was never seen again in the movie.
When Charlie first jumps out his window to go with Jasper, he is barefoot and doesn't have any sandals on. Then when they arrive at the tree by the river, Jasper suddenly has sandals on.
During the cricket match, when Charlie was talking to Jeffrey , Eliza was reading books under the sun but few moments later when Charlie reached near Eliza, she was seating under shade.