We have this thing, in photography. There are tolerances for bodies, and for lenses. So, the lenses can be within say +/- 0.5% for what they say it's specs are. The body, also, has a tolerance of about the same for it's acceptability.
If it so happens that the lens is - 0.5% within tolerance of the targeted spec and the body is + 0.5 % within tolerance of the targeted spec, guess what? You get issues.
This is what happens when you have different components with different tolerances that eventually are paired to work together.
There may be something like that, going on here too.