Hysteresis is the inability of an object to return to the same position. When the dampers modulate in accordance with the climate conditions or predetermined schedules, they are unable to reset back in the same place. So, it is conceivable that there could be a lot more OA entering the unit than you realize, causing the system to work harder to condition the air and increase energy costs.
Dampers could bind or actuators could slip as well, and there would be no way to know unless you had someone go on the roof everyday (obviously not a realistic solution). Just like with hysteresis, this issue could cause serious issues to energy consumption and expense.
All of these factors could lead to serious over-ventilating, which would lead to drastic energy expenses.