Maurice and Dave stop and get out of the car, a truck drives by, knocking the left side-mirror off. When they get in the car again and drive off, the side mirror is on the left side. When they stop later on, the side mirror is gone.
After losing one of the yellow lead cards out the window, they pull over and look for it and a semi drives by and knocks the side view mirror off the drivers side door next seen its intact again, then when they show up to the last leads house its off again.
When Maurice and Dave get to the woman that belong to their last address card, she excuses herself for a minute and closes the door. Right afterwards, when the two talk to each other, you see the same door half open in the background.