The three laws

Three Laws Safe.
You see that sticker on every robot we sell.
It’s not only our motto, but it’s the law.
If a robot causes so much as a scratch or a stubbed toe, we take it to the shop and tear it down.
Bad programming? Corrupt files?
A bit flip, caused by a cosmic ray?
Those used to happen a lot.
A one flipped to a zero can cause all kinds of mayhem.
So we put in triple error-checking. Everything runs three times.
Two out of three calculations wins the argument.
Comic rays don’t strike twice, or, do they?