So while testing I have about 4 nodes (local) running and if I were to stop them all, and then come back a few minutes later and restart them, with the exact same --base-path, I'd get this error :

WARN tokio-runtime-worker babe: Error with block built on 0xe8e8..a5ff26f911: ClientImport("Unexpected epoch change")    

My question is what does this error really indicate, and when does this occur? Is this error common in babe based chains (or is my chain weird)? Does it imply that if all nodes in a substrate blockchain were to go offline, it couldn't be restarted?