Our 8 presets would work and stop working at random times. We took the car in to get a couple of recalls done so we mentioned this to the service technician. He reported that there was nothing wrong with the car and that each set of keys had separate presets associated with them. Who knew? So we have programmed both sets of keys to have the same presets.
I share this info in case there are others who didn't learn this during their briefing on vehicle features.