1) The radio in my 2009 Lexus ES350 periodically goes silent. This happens, typically, every fifteen minutes or so, and the silence lasts anywhere from a few seconds to several minutes. This happens in all the different modes (AM, FM, SAT, AUX, etc).
2) Occasionally, but not always, modes disappear --- so that when I am cycling through the various modes, SAT might be missing from the usual AM/FM/SAT/AUX sequence. This seems to occur in close temporal proximity to the silences.
3) There is an equalizer screen, where I keep both bass and treble set somewhere near the middle. If I visit that screen during one of the silences, bass and treble are turned all the way to max, and cannot be changed. Once the silence ends, they are back to where I had them set --- so that all this would be invisible to me if I didn't go looking for the equalizer screen during a silence. I mention it only because it might give a clue to the underlying problem.
4) The local stereo shops won't work on factory installed equipment.
5) The Lexus dealer is baffled. They think the most likely culprit is the amplifier, but that a plausible alternative is the "head unit" which is tied into both the radio and the navigation system.
6) They tried swapping my amplifier with the amplifier from another car. During the time of the swap, they were not able to replicate the problem on either car, but they admit they only listened for a limited time, and the problem occurs pretty unpredictably.
7) Their suggestion is to replace the amplifier, at a cost of (if I remember right) about five hundred dollars. If that does not work, the amplifier is non-returnable. The next step would be to replace the head unit, at a cost of another eight hundred dollars or so --- assuming they can find a refurbished head unit, since new ones are no longer available.
Question 1: Do you believe the problem is likely to be in the amp, the head unit, or elsewhere?
Question 2: Should there be a cheaper way to fix this problem, short of completely replacing expensive equipment?