I would suppose that Toyota would greatly prefer to find out that this is a software bug— and therefore a software fix. Flashing new code into the computer is likely far, far less expensive to fix than a mechanical or design flaw.
But in any case, isolating the root cause(s) of extremely rare failure(s) is harder than it sounds.
Could be RF interference. There is a ton of RF energy floating around, especially in urban areas and along roads. RF interference wouldn’t be hard to prove one way or the other, though. Half an afternoon with Toyota, a signal generator and PA and I could determine fairly conclusively whether or not RF was the culprit.