Motorized linear potentiometers are a rare, exotic, and just plain neat input device most commonly found on gigantic audio mixing boards and other equipment that costs as much as a car.

After becoming frustrated with drift in the potentiometers, he set out to outfit the entire rig with custom-built encoders. [s-ol] designed the rotary-encoder based boards around an FPGA.

But more often than not, it's because of the potentiometers, which track the joystick's position through physical contact. Over time, this friction damages the potentiometers, thus causing drift.