As Jimbo says, and as I have stated many times, sequential HGF is a common occurance on K series, whether that is indemic (as I believe) or poor workmanship ( as James believes) is irrelevant. It happens, and all too often .
It happens all to often as you said. There is sometimes no obvious cause ether
The problems with an engine overheat can multiple. The head could be warped to it's maximum tolerance, combined with 1 liner at it's minimum hight with 3 others at there maximum. Then the fact that the MLS gaskets don't compensate for this like conventional gaskets. All these things are fixable but it's an engine out job which is time consuming and if any machining needs to be done can be costly too.