Earlier models have been found to have severely damaged keyways that were apparently caused by stretched timing belts that developed an harmonic slap in the timing belt slack. I suspected that the crankshaft keyway was not properly hardened for such damage to occur. The crankshaft bolt on one truck had repeatedly worked loose and was the cause for it being brought to me. The bolt would likely never work loose if properly tightened and even the weakest thread locking compound used. You might be wise to get a second opinion. It is very difficult to do more than speculate here. I can’t be certain of the cause of the damages that have been repaired on the 3.0 cranks repaired here.