Can't help with a fix, but I can confirm you are not going crazy...
This summer I drove from Denver to Detroit and back 3 times, and every time I went past a 40 mile stretch near Ogallala Nebraska, the radio would jump from the (only) classic rock station 94.3 (or thereabouts) to 104.something, a country station, bypassing several stations in between. ( not just the next signal on the dial, and both stations had strong clear signals)
Sometimes passing a truck would trigger it, sometimes it was entirely random. Sometimes it would stay on the rock station for 5-6 minutes, sometimes only seconds, but it WOULD NOT hold the station. Bizzaar and maddening.
Don't know what the cause was but it was definately localized.
Often when it is cold outside, the Infinity head unit won't function at all and only displays "Chrysler" Turning the car off and back on after running for 5 minutes re-animates it.
I think the stock Infinity unit is junk IMO, but mine still works MOST of the time.....