This is the worst review that I have seen so far on the Titan diesel. I hope that it is an isolated case: http://www.caranddriver.com/reviews/2016-nissan-titan-xd-long-term-test-review
Some engines just have problems, even when new. Our company has many new trucks and while just gas motors some are reliable and others are not. Even though they are all the same truck and motor we've had head gaskets blow, camshafts get wiped and transmissions fail while others have close to 60k miles and not one problem.