I am making shipments to my clients, of various circuits that I manufacture, and I find cases in which the product is installed and it does not work for them. I test everything before shipping.
Specifically, a board with a Kinetis MK66 microcontroller, the customer returns it to me, I test it and it doesn't even allow programming, it's locked.
Two other cases, with Raspberry units that the video output does not work. It is not that it has failed them after a while of use, it is that as soon as it arrives, they install it and it does not work, when I here check everything before sending it.
And since there are already several cases, and not all of the same board, one with my board that has a Kinetis MK66, and another two with Raspberry video failures, I don't know what to think about. The only thing I can think of is that the X-ray or electromagnetic arcs from Customs can damage the circuits, and if I could avoid it by putting the boards inside antistatic bags.