Continuity mistake: When the truck arrives at 5 Pointz, it rattles when it stops, prompting Dylan to put his left hand on the inside door. His hand appears to be level with his shoulders at first, but when the shot cuts, his hand is much higher up, before moving it away from the door. (01:32:00)
Continuity mistake: Whilst watching the Horsemen's YouTube video in the back of the truck, in the shot of Henley saying "Remember the name Jack Wilder when you see us live. 5 Pointz, Queens, seven o'clock," Dylan can be seen in the corner of the frame, with his hand away from his face. The shot then cuts to focus on Dylan and Cowan, and Dylan's right hand is suddenly over his mouth. (01:31:12)
Answer: The mirror was inserted at an angle, so that the reflection was the ceiling and not what was in front of them. It's the same principle for how periscopes work.
Bishop73