Not an expert on these but they are known to lose parameters with power issues. Our tech support suggests archiving the EEPROM or recording all parameters, they also have a bulletin on installing a delay on timer feeding the XM16 plug to allow power to stabilize and any time you cycle power, XM16 should be out until power is back on.

I would compare every parameter to the other cars, especially the car # in group. I fact I once had only one car answering calls in a duplex and the car # in group was right but changing it, cycling power, then changing it back and cycling power fixed the problem as if it could not recognize the parameter value.

On the other hand, a change board LED coming on when you push on the board is a bad sign, sounds like a bad solder joint or something.