Solder joint on a circuit board shrinking and opening up? I seem to recall that even the space program had issues with a satellite when they switched from lead to non-lead solder.
Take this as an opportunity to buy a double DIN kit and a decent radio and replace it.
I still have the old AM/FM/Cassette radio (and I don't listen to the radio anyhow) but I did make a cell phone holder that fits in the cassette slot. Its a little bouncy but works quite well. I didn't want any holes or glue on the inside of the truck, and wanted it up where I could see it and not need to look downward to see it.
Charles