It has not happened again but if I have to make a guess my ignition key cylinder has some play so it could be the ignition switch didn't fully return to run and caused that hiccup. If the amp shut down the head unit would still be on. Like I said, I did have an issue a few times with the face plate not making contact but I cleaned the contacts a few weeks ago and that seemed to resolve that issue. This time removing the face pate and putting back on didn't help. The radio is an old alpine 9835 but I'll never get rid of it and I do have a backup 9835 that is in my jeep.