I have noticed the same, by happenstance. I rarely test the controls and exercise rudder with the engine off. With the engine off; in exercising the rudder from stop to stop the noise was noticeable. Was done with pressure on both pedals to keep both cables taut.
As such, I removed the baggage bulkhead panel and determined the rubbing noise was coming from the right ruder cable rubbing on the bottom of the plastic bushing in this bulkhead. Checked the bushing surface where the cable rests with my fingernail and found no wear.
Had others do the same, and half hear the rubbing noise and half do not. Changed my checklist!
Jim........ did you find the same or something different, your post is not detailed enough for me to understand.