Plot hole: The energy weapons in this story fire a series of small red bullets, which cause numerous problems. For a start, the guns appear to have seven chambers, yet the bullets start from the same point; as they are separate bullets, surely the most minor of movements would mean they wouldn't emerge in a straight line. Later, when the Doctor steals a cart, the bullets are coming quite a distance towards the screen but the bullets don't get any bigger. Also, in the same scene, the Doctor passes through the area they seem to be travelling, yet the bullets just continue to pass in front of him.
Continuity mistake: When the Doctor enters the desert room in addition to his coat, he is wearing a brown waistcoat with a white shirt underneath. When the shot cuts away and the back to the Doctor, we see him take off his coat but he is no longer wearing the waistcoat. Later when he collects his coat after the acid bath scene and he starts to look through the wardrobe for a disguise he is mysteriously wearing the waistcoat again.