At approximately 18:00 and before Vito paints the living room faint grease spots or blotches can be seen on the wall to the left of Laura's right shoulder; this is not the spot Rob messed up. At approximately 21 minutes the same splotch is still visible now above Vito's right shoulder after he painted the room. This is not Vito's signature; which is on the same wall at the baseboard.
When Ritchie exits the house to go next door, he walks straight to the exterior corner of the house rather than straight down the sidewalk. It seems apparent Larry Mathews was exiting between gaps of the set.