Can anyone tell me what the most likely cause would be for a car radio to
lose its sec code setting everytime the car ignition is turned off?
Background:- the radio has been functioning normally for the 13 yrs of its
life but it has just come back from having its front fixed at a
panel-beaters. The bty would have been disconnected for a while but the
damage was only to the bumper section so no re-wiring would have been
necessary. The car is a lowly Nissan Bluebird with the std radio fitted.

TIA.