There's always the possibility that it noticed just how useful it is and decided to give up
. OK - some of them have a fuse on the circuit board. Most of them have power available all the time on a bus bar on the circuit board. Pressing one of the buttons supplies power to the circuit chosen, and sometimes causes the board to flex, eventually breaking a land. All it takes is a hairline crack.
Check the board carefully after determining that you DO have 12v at the bus.