that would be the sound of the brushes going across the com bars on the armature.
usually when the motor is stalled or over-rev'd it can heat up the armature and cause the resin and insulation holding the com bars in place to soften and the com bars will raise up. When this happens the brushes will make that noise when they move across the uneven surface.
What happens when this occurs is the brushes may jump off the surface of the armature briefly and cause the system to trigger an error, usually an open motor circuit error.

On rare occasions you can repair the armature but most of the time the damage is irreversible and the armature has to be replaced because once the com bar separation has occured it will continue to get worse. Cutting the surface back down even does not help as the bars will keep coming out.

You can get a brush stone set and clean it up if its not too bad and buy yourself some time but in the end the armature will probably need to be replaced.