The stiffening rods wouldn't have had much of an impact on the truss rod at all, but if they were stiffening the neck correctly, the chance of having to adjust the truss rod would have been reduced.
After 18 months I would assume they would. It would not be reasonable for a truss rod to fail in that time. However, there is the issue that it is hard to prove user error, without looking at it.
Certainly following the link that was supplied, that truss rod failed due to manufacturing defect, but hard to prove without having already taken it apart.
Note that they also have titanitum truss rods as well, rather than what appears to be steel for the mzk ones.