I have the same Issue!!!
I hardly ever post here but I saw this when doing a search on google.
I have a Sony TRV-310 and since last year I get the code 21:00 meaning it has due on this so called sensor.
It has to be an error, does anyone know were it is at so I can wipe it? the camera is 100% useless, and I don't know if my next camera will be a Sony, I never seen other brands have this isse.