Deliberate mistake: The Virtuoso (up several stories in a building) would not be able to hear what the boy and his mother across the street were saying. The boy even started to say "Hey, mom" when he was still exiting the building. (00:11:41)
Deliberate mistake: When James started to fall off the ladder, he tried to jump to reach the other side. Thom grabbed his right hand with his and was able to pull him to safety. James' weight and the force with which he jumped and swayed would have most likely resulted in James pulling Thom over the edge with him, and both being seriously injured or killed. (01:22:26)