I had the BU Camera issue today, when I backed out of the garage. The camera on and off button did NOT work for me, neither did a screen reboot or anything else that I tried. However, I did not try the icon many times, just a few times to no avail.
Anyway, I live in Auburn CA and was driving to the HFT in Rocklin, which means I drive right pass the Tesla Service Center. So I stopped there to ask them about it. I was told many others have reported the same problem, but is always intermittent and will come back on by itself at a random time & if mine doesn't, to make an appointment with them.
They are not yet certain what causes the intermittent problem, but they assume it will probably be fixed in the next firmware update.
I was at the Tesla place no longer than five minutes. I backed the car out and my BU camera still did not work. I get the lines, but no view, BU camera screen otherwise dark.
So then I completed my trip to the HFT in Rocklin. I was in the store for at least a half hour. When I got back to my car, the BU Camera then worked perfectly and no more problems with it today. I didn't do anything other than put the car in reverse when it did work again.
Today was the only time I had the issue and today was the fist time I drove the Tesla M3 in at least a week.
-Don- Auburn, CA