It's not unknown for spacecraft to come back to life. One of the ham satellites, AO-7 for example, launched in 1974 became unreliable in 1981 when the battery failed short, and not long afterwards it completely fell silent.
In 2002 one of the cells went open, presumably from temporal chemical changes and continual electrical stress from attempted solar charging.
As a result, when in sunlight, the satellite still operates to this day as an analogue voice transponder. There's no on board computer, it's a bunch of CMOS logic controlling it, so it's pretty dumb. When it goes into eclipse, the limited state held in the CMOS logic is forgotten and it's a crap shoot what analogue transponder mode it comes back up in when back in sunlight as a result. But it still works!