@mntmn@Laberpferd@timonsku hm, but if that ESD diode became self-sacrificial, that would either be a severely underdimensioned protection, or a serious ESD surge that I wouldn't expect pcbway to have on series prod.
Q: is there a reasonable way you could estimate the worst-case negative pulse amplitude caused by opening a keyswitch under load? How much current do you put through your keys while scanning the key matrix? What's the (order of) inductivity of the longest trace?