I wonder what happens when there is a bug in the sensor thing. ...
That would probably be a real bug ...
... As there are bugs in all cars with electronic that we have these days, that could be much more dangerous than problems like the ABS that disconnects sometime (a problem that I have on my 206).
The problems today are less often the electronics or software, but the connectors. If proper material would be used, avionics and military electronics show how to do it, cars were less often grounded by defunct circuits. But reliable cars are bad for the economy! Who would pay all the car mechanics and spare part dealers?
For safety relevant systems redundancy is the key word. You have that in trains and airplanes for decades. Systems with identical functionality are installed in triplicate or more, often using not a similar, but different design, to avoid failure through design faults.
Once fully autonomous vehicles are available for mixed traffic, i.e. traffic where still people are driving manually in the same lane, the systems will be extremely reliable. But that is still some years into the future. My estimate is that mass production will see autonomous vehicles around 2020.
... would then be the Peugeot 2-0-12 ...