When all are gathered and Luke is explaining his plan, a male student is trying to persuade him of the futility of his intentions. From the front view he is standing and a lot taller than Luke. But from the side view, he is sitting an is almost the same height.
All through the ATMOS fog segments outside Donna's house there is a car with its lights on opposite her mother's car but when the fog is clearing it is gone.
At the beginning of the episode, Donna's mum smashes the front window of their car. However, car's windows are triplexes: 2 layers of glass, glued to a single layer of plastic, so they don't simply collapse, as shown. (The whole point is to prevent the crash and minimise injury from glass cuts.)
The Sontarrans are a clone-stock species, all physically identical, yet in several scenes of them marching, it is obvious there are some Sontarrans who are much taller than the others.