The -w parameter ist the path to your webroot, the "root" - value of your nginx - server.
You have new certificates created 2018-10-04, --dry-run has some limitations.
So update your certbot and check, if the renew 2018-12-04 works.
Please read that:
Note: Although --dry-run tries to avoid making any persistent changes on a system, it is not completely side-effect free: if used with webserver authenticator plugins like apache and nginx, it makes and then reverts temporary config changes in order to obtain test certificates, and reloads webservers to deploy and then roll back those changes.
You have such a "recovery error":
--dry-run may produce errors used with special configurations (or with your too old certbot), so you should ignore such a problem if you have active and valide certificates.
--webroot may have less side effects then --nginx.