Had C-band satellite as a teen. All the good channels locked. But if the satellite Spacenet 1 transponder 18 was locked, you could “fine tune” the reception from say, Galaxy 3 transponder 18 by holding the step up or down button, and manually swing the dish halfway across the sky to the same position where Spacenet 1 is. As the descrambler thinks you are watching a different satellite altogether, there is no more lock. And since you never actually visited a bad channel, no way to tell with history or last buttons.