I turned on the debug mode on the logging and tried your request again. It appears that the CAA request is being redirected once or twice to different servers. My guess is that the information and images have not yet been replicated on the redirected target servers, and thus the problem ultimately ending up in the 404 Not Found error. I suspect that eventually the replication will catch up and the problem will disappear.
In any event, it appears to be a problem with the cover art servers and not with Picard.