In the trailer when Ruth & Wyatt are talking, the pack of beers is changing position between shots.
Wendy always drives a light-coloured car, but the car she and Ben take off in is dark-coloured (though not dark). This especially apparent in the scene when Wendy discovers Ben calling someone (it was Helen) and breaks down. The car is most certainly dark-coloured. Yet when she finally gets back home she is in her light-coloured car.
She might possibly have - for whatever reason - switched to another car but this is not obvious at all. On the face of it the car Wendy is driving goes from light to dark back to light again.
Right before Jonah shoots the window, he chambers the shotgun. Since he had already chambered a round right before that when he confronted Helen, the first shell would have ejected, but it did not.