Michael I trust you are not an employee or an associate of Bunq.
This is the community forum, employees have a special blue badge. Everyone else is just a user, including purple badges like me. Sure, cards get lost in the post. As for why exactly, that's hard to say because cards are sent all over Europe and as Bernd already said, none of the dozens of different postal companies that might be involved is willing or able to exactly research why some letters don't arrive. Sure, you could send the cards by registered mail (and in case of the higher value Metal Card, this is exactly what is done), but in almost all cases it's much cheaper to just send out another card instead.
That said, to answer your initial question, in all the years at bunq I never had a card not arrive at my address in Germany.
