Originally posted by jatrax if it is so easy to detect
Maybe, but I think it is not so easy to correct it.
They probably can only repeat the assembling process the same way it was done in production, and hope it will improve. If not, another try, and then maybe replace parts.
I guess we are talking of variations of not much more than 1 mikron where the lens elements are sitting.
And in some cases probably also the case may be the culprit.
EDIT:
I know all this can be done in QC during production.
Leica was known to do it (at least in the past), but you payed for it.
And I heard Pentax does this kind of expensive manual checking only with Limiteds.