Then there's the old story about Japanese manufacturers.
The 1,000 part order is sent with instructions for a very high QA rate – 0.1%, or 1 in 1,000.
The stock arrives in two lots, one large and one small box, with a note. "We don't know why you asked us to make one that is broken, so we sent it in a different box so you can find it easily."
QA these days is simply price – you get what you pay for (usually). Cheap = no testing. I brought some cheap (<$20 vs $100) temperature controllers off eBay, one didn't work. A bit of soldering on the display got skipped on that one… easy to fix, but it was obviously never plugged in before shipping. Nice little units actually. Sound like the mills!
Tony
Thirty years ago when my company imported a lot of electronics from China (Hong Kong), most double side PCBs made used plated thru holes and a good solder joint should have been made. Probably a bad board, boards these days aren't hand soldered but are soldered by using a wave soldering machine. The Plating process could have been poor or the board wasn't preheated enough prior to the wave soldering. Your board would have tested fine until the eventual joint failure. Failures do occur and these kind are harder to catch. Most Chinese manufacturers then accepted a 5% failure rate as a satisfactory rate. My contracts called for a 2% QA failure rate as being acceptable...... had to work with them to keep it that low....
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