I know that, that's why if they stop I think of them as pots, if they don't stop then I think of them as optical encoders.
And since the one in question is continuous as in it sends a lot of pulses per turn, they must not be optical since those ones cost 10x more than the mechanical ones and the magnetic ones cost 40x more than the mechanical ones.
Now if it was the Scale knob, that has 19 pulses per rotation, well, that one can be done with a cheap mice like optical encoder. But for the fine grain position knob, it must be mechanical.
Edit: Those 19 pulses might be detents like you mention, but they correspond to the input. But that could be part of the counter hardware.
In any event, it could be the connector to the main board that is at fault or the chip behind the encoder. Most likely they'll replace the input board and call it a day.