It's never spontaneous. Banks and transaction processors lose money regularly, they just don't expose merchant fees and chargbacks to the buyers directly, but w

It's never spontaneous. Banks and transaction processors lose money regularly, they just don't expose merchant fees and chargbacks to the buyers directly, but when you remit money to another banking system or want to cash out your balance, you are exposed to those fees and times and limits. Bitcoin and lightning network exposes the end users to all the potential security issues, but gives finality and no bank bailouts in return.