This is the first case I have come across where the phase detect autofocus (viewfinder) is good but contrast detect (Live View) had a problem. The typical reported case is the reverse. As such, you might want to provide some additional information regarding your testing and maybe post some examples. As far as I understand, the contrast detection uses the actual sensor data and thus there is no real "AF sensor". In particular, there is no left, center or right AF sensor. In any event, if you sent your D800 to Nikon, I don't see that it would simply be sent through the "Left Focus" procedure since yours is not the issue that everyone else is experiencing.