From time to time I set some of the pre-sets for the AM radio dial (and even less frequently, the FM dial). Here's the mystery: over time, the pre-sets disappear! They revert to being marked "Empty." Why? Are the firmware updates erasing 'em? Something else? It's really annoying to have to go back and re-set them. In every other car I've ever had since beginning of time, a radio station pre-set setting is forever. Anyone else noticed this in their S?