What Happened to the Boeing 747?

Seven years before this incident, the 747 was involved in a tail strike at Osaka International Airport upon landing. The back part of the plane that contains all the pressurized air in the cabin had been damaged and needed to be repaired. But instead of using one plate to call it a splice plate, they use two splice plates that were parallel to the crack. And what happened was, since they cut it into two plates, it brought the integrity down to 70%.