In the final chase scene; in the long shots of the car it has a windshield, but in the close ups there's no windshield.
When Curly tosses a glass mug full of beer at Larry, Larry catches it but accidentally spills it on Moe. When Moe steps over to confront him, the mug has changed from an actual glass mug to an obvious prop made of breakaway material so Larry could be hit over the head with it. Update: Moe ends up being a lot wetter than he would be from a mug of beer.
During the car chase at the end the bad guys and the Stooges pass the Dixon Feed Store twice.
At one point Moe does the eyes-poke on Curly, and the choreography is performed very poorly so the phoniness is blatantly apparent.