There's a variety of motion mechanisms that can't be backdriven. A worm drive[1] is a common one. Alternatively, they could simply have a external lock on rota

There's a variety of motion mechanisms that can't be backdriven. A worm drive[1] is a common one. Alternatively, they could simply have a external lock on rotation that's engaged when someone's not actively moving the cells. 1: https://en.wikipedia.org/wiki/Worm_drive https://en.wikipedia.org/wiki/Worm_drive