I've noticed that the buttons on these radios, when not pressed for a while, become very 'sticky.' I had the same issue with my "AutoSET" and "CD" buttons on my radio. I would never press them, one day I accidentally pressed AutoSet instead of CLK, and the damn button got stuck pressed.. and took a while to come out.
Mind you, I have a different radio than you're '03, but I doubt much has changed in how they make the buttons.