When David gets out of the crevasse, the sky is gray and cloudy with rain, lightning, and thunder. When the tree falls toward David, the sky behind is crystal blue.
When Michael is nearly killed, the dustbin jumps from the sidewalk to the driveway between shots.
Michael's birthday cake and candles change between shots.
When the car almost hits Michael, his father watches from the open front door. The door was closed in the previous shot, and the father never opened it.
Near the end of the film, when David digs the hole to bury the monkey, its mouth changes from open (baring teeth) to closed and back again.
When David gets into the shower, he is obviously wearing underwear.