Just want to make a couple points about QA:
1. Samsung sold 4.5 million Note 4 units in their first month. They've got to be up to 10 or 12 million by now. They can't check every feature on every phone before it leaves the factory...there's just not enough time or employees to do that. (Can you imagine the size of that checklist?)
2. Electronics are delicate and very, very tiny. There is just so little room for error that any manufacturing defect can introduce problems. Which leads to...
3. Samsung is not the sole manufacturer of this phone. The main processor and GPU are made by Qualcomm (US variants), the screen is made by Corning, the camera is made by Sony, the GPS chip is made by Broadcom, all the s-pen functionality runs on Wacom technology, the audio processor is made by Wolfson, the barometer is made by Bosh, and a whole host of other companies like Yamaha, Maxim, TDK, TI and Murata contribute parts. The quality of the phone is highly dependent on the quality of each of these parts, and in turn, on the QA processes of each of these companies.
So if 100 bad GPS chips come off the assembly line at Broadcom, you get 100 defective Note 4 units with bad GPS functionality.
4. The phones pass through a lot of hands before they get to you. They are partly assembled by machine and partly by hand. They are boxed, warehoused, shipped all over the world using a variety of shipping services, warehoused with distributors, shipped to vendor warehouses, distributed to individual outlets and handled by the people who stock the shelves. At any point, a box of phones could fall off a truck or high shelf. While the packaging will prevent most damage, a box could fall at just the right angle to break a piece of solder or crack a lens. Angle is everything. How many of you have lifted heavy crap all over the place only to hurt your back with something relatively light because you "picked it up wrong"? Same principle.
So basically, what I'm saying is that these phones are very delicate devices and there are a lot of potential reasons why one may end up in your hands not operating at 100%. I don't think it's fair to blame Samsung's QA when so many factors are outside their control.
Actually, now that I think about it, it's damn near a miracle any of these things work in the first place. Must be magic.