ONE> About twenty minutes into the movie, when Danny goes to the basketball court (before the flashback).
TWO> As he is leaning over the chain-link fence there appears to be a grey thing on his right elbow...
THR> When the camera does a shot from a distance away it ceases to exist...
FOU> And it comes back again when the camera gets close again.
FIV> Thats a slip up by Johan Anderson.