Difficult to assess but I would suggest taking a look at the month and day you have selected. In the larger model, you have January 1st selected. You may be limited due to total solar hours on that day, compared to the larger range of solar hours on June 1st, which you have selected for the smaller model.
Could the problem be the location of the model in World X-Y? When things are far from the origin, Rhino's native rendering functions suffer. You can see evidence of this even in the Brep wireframe display.