If you are in a Quality or Advanced Rendering style, whenever you change your view, the program goes to the current Draft render style, then returns to the previous render style. There's a reason for it, but I can't remember just what it is at the moment. The "Red river rural.TCW" file didn't have any materials assigned when opened.
re: …How can you tell?
The difference between Draft and Quality/Advanced are the jaggies found in Draft.
Designer, Deluxe, Expert, Basic, Platinum
Windows 10, 64-bit