When Matthew argues with the old man, it is sunny out. As he goes and talks to Jerry, it suddenly gets much darker.
Right before George was about to park a car, it was shown that they were in a wide street, with (at least) 3 lanes in their direction. So, later when George and Mike were arguing about the parking space, it doesn't make any sense that a truck driver wouldn't be able to pass around them.
George starts to get out of his car to confront the parking space thief, but in the next shot he is completely inside the car again.
George (Jason Alexander) and Elaine (Julia Louis-Dreyfus) are shown exiting the car on a long shot, and then again on the close-up.
When Jerry (Jerry Seinfeld) decides to put his car into a garage because the fight starts in two minutes, the car door is left ajar, but when the camera cuts back to it a moment later, the door is closed.
When George pretends to shift the car into reverse, he pretends it's a column shift, whereas the BMW model he is driving is actually a console shift.
When George and Elaine are in the car and the camera is pointed down on the windshield, they're obviously on a soundstage. If you look in the corners of the shot you can see the plain-white wall, when they're supposed to be driving back to Jerry's apartment.
When Elaine goes up and take to Jerry a boom mike can be briefly seen and, as the cameras draws back, can be seen more.