Although no passengers are picked up or dropped off, the rear door handle on Bud's taxi is in a different position from scene to scene.
What happens to George's baggage after he and Alex climb into Bud's taxi at the Airport? Bud climbs into the taxi and leaves their baggage right there on the ground! (A big brownish bag that George was carrying that falls over to the back).
George gets upset when the Post Office won't mail his film. He complains about "letter day" causing the problem. However, since it is a Sunday, if it was not letter day the Post Office would have been closed anyway, and there would have been no pick-up regardless.
When Bud says goodbye to Susan at the Post Office, he refers to Aunt Henny as 'Aunt Hayley'.