You may have entered a time warp.

Had a similar experience a decade ago with my first (8-channel) GPS-20.
Over the Diamond Range during a flight out of Tonopah, the audio
vario changed to a theme from The Rocky Horror Show, and the GPS logged
me being back in 1946. Since I was in the middle of the Great Basin, I
didn't notice any change in the scenery during those 4 seconds.
Others thought it something to do with Area 51.
Jim