In the scene where Gene arrives at the land house, the rear-view mirror inside the Quattro keeps appearing and disappearing between shots.
Near the end, at the airfield you can see that the Quattro destroyed by gunfire is not the same that the one who was drove through the runway (the one used throughout the series), you can clearly notice it in the shape of the wheels (rims), they are similar but not the same.
The Vauxhall used by Alex to drive to the land house can also be seen at the airfield. However, as Alex Jim and Gene all drove back together in the Quattro, it is unclear how the Vauxhall got back.