Even if it is very rare it's UNACCEPTABLE!
It may ruin an once in a lifetime shot. If someone cannot count on their equipment then the equipment is not worthy.
It would seem that as more modern and capable cameras are made reliability would improve and this is clearly not happening.
This (or anything similar) has never happened on my 5DMkII.
So,Most photographers are very happy to have 50% of their images become keepers. You must not be willing to accept one of 15,000 that are not perfect.
What are you going to do if one day the photographer goofs and you have a poor image? Send him back to the factory?
This could be easily caused by opening the battery door before the camera finished writing. If so, send the photographer back, one of 15,000 is unacceptable.