Leica QC issues
This topic often crops up on various Leica mailing lists and online forums. For example, see <Greenspun.com: #006dmp> to read a Oct 2001 thread on this topic in the greenspun.com Leica Forum.
All the complaints iterate around the same basic riff: "I paid big bucks for this stuff, anything less than perfect is bad enough, but faulty gear is just unacceptable".
Which of course is completely reasonable and fair. But rather than whingeing about it, be smart and (1) always carefully examine everything you intend to purchase, and then (2) be prepared to make use of the generous Leica warranty if you do spot faults at a later time.
If you buy via mail order, then let the merchant know beforehand - in writing - that you are more than prepared to return the equipment, and if necessary, even stop payment on your credit card if you detect the slightest fault. That should keep 'em on their toes!
Yes I know we shouldn't have to do this, but that's life. By way of comparison, my Omega Speedmaster Automatic wristwatch failed twice during its first year - so I guess Leica aren't the only ones with QC problems when it comes to finely tuned mechanical instruments. That is after all why these things come with warranties.