agreed with ZF QC + assembly are not the top rank compare to their rep-ability.
I have few ZF in past and now only one I keep, all of them have either crooked index, dust, rotor stuck, etc but all of them went to watchsmith for porper check and clean. After that they all run smoothly without any problem. Sold most of them now and only keep the 5007, still running strong and finger cross wont have any problem in near future.
From reading the thread, seems like lots of "Trusty" came up and for statistic wise might be the seller had bad QC when selecting watch from the factory. My understanding when I got my ZF from seller (watchbus - Not TD here), he did actually spend time picking / choosing the good one and rejecting a few before even QC pics for me. So, i think also down to the dealer effort of the screening the bad one out and not just pick one from box and there you go QC done. (Pick the less problem watch instead of full of problems, i admit that almost all ZF pieces have quality issues)
I've passed many feedback to dealers i bought from about ZF issues and hope others will do the same too. or just don't buy ZF at all until they fixed it.