When Klink came back to camp in his staff car, the driver was not Schultz.
Hogan asks Newkirk to set up a switchboard to intercept phone calls. There has been a switchboard doing this ever since early in season 1.
When Colonel Hogan and Hedy Von Behler are talking outside, she mentions how very cold it is. Hogan even gives her his coat to wear. However you don't see their breath in the cold air when they are talking.
Hogan and his men are working in a rail yard. There is a fifty-five gallon barrel nearby with hole cut in it and a fire inside where Hogan and Schultz warm their hands. There is snow on the top of the barrel.
In scenes supposedly at night, there were heavy shadows on the buildings behind the men, from the production lights. If this were actually night, there would be no shadows. If there was a full moon, the shadows would not be at that angle, and they would not be that heavy.
When LeBeau closes the safe in the General's office the door begins to open after he has supposedly locked it. He locks the safe by spinning the dial. In actuality he would need a handle to lock and unlock it. Spinning the dial would then prevent you from opening the door until the correct combo was used. Thus it was not a real safe.
When Hogan and Newkirk are outside near the barracks, there are heavy shadows of the men on the barracks wall. The shadows are too heavy to come from sunlight, and not at the right angle. These are shadows from production lights.
It is not explained how Hogan got the plans to the house. If he drew them himself, or were given to him by Hedy, this was not mentioned.