Diagnosis
Foreign material is caught in the rotating mopping pad assembly or the main brush. The most common cause is hair wrapped around the central shaft.
How to Fix It
Turn the robot over. Remove the water tank and mopping pad frame. Manually rotate the gray plastic disc that holds the pads. Inspect the central bearing area for hair and debris. Use tweezers to remove all wrapped material. Also check the side brush for obstructions.
If That Didn't Work
The gearbox for the mopping pad oscillation has failed. This is a mechanical fault. You will need to contact iLife support for a replacement oscillation module or main chassis.
Heads Up
Running the robot with this noise can strip the plastic gears completely. Do not use it until the obstruction is cleared.