Same here, was very pleased with Caddy so far, but it being tightly coupled to LE being up, despite having certs cached is a no-go for our production systems and if this stays like that, would make me go back to nginx for the services I've used caddy so far.

edit: looks like the dev added a fix to only refuse the start if the cached certs are dangerously close to expire. that satisfies me and I'll be continue to be using caddy.