When the Lone Ranger and Tonto are overtaking the stagecoach carrying the deputy and undercover officer "Slim Roberts", the deputy is looking 90 degrees to the right from the coach interior at the Ranger and Tonto, while the exterior shots show the Ranger and Tonto riding directly to the rear and even slightly to the left of the stagecoach.
At the end, in the Empire office of Marshal Dixon, Deputy Clifford calls Slim Roberts, Mr. Robertson.