Imagine taking out your phone and wallet after a long day of work and putting them side-by-side to each other. One day, by chance, perhaps on your cluttered computer desk, you decide stack your gorgeous Lumia 950 on top of your wallet to save space, only to find a rather odd reaction: a repeating string of NFC detection sounds played together as though the phone is puking out NFC detections. This is best illustrated through the video above.
As it turns out, the culprit is a Clipper Card in my wallet, used as a pay card for public transportation in the Northern California Bay Area.
This behavior, to my knowledge, gets triggered whenever your Lumia device has NFC detection enabled, and your phone's screen is not locked (or depending on your settings), and it can be triggered by any device that features some kind of NFC receiver, including Clipper Cards or even other Lumias.
This problem has been around since the Windows Phone 8 days as well, as it gets triggered even on Windows Phone 8 powered devices like my Lumia 1520.
While most of you will never encounter this problem, it's a surprising hassle for me because in order to save space, I often stack my devices on top of each other. For once it seems like having too many Lumia devices to play with, has turned out to be a bad thing.