I actually got this error when trying to reconfigure the same index pattern that used to work
Oct 24 13:23:04 node-79-ny kibana: {"type":"response","@timestamp":"2017-10-24T20:23:04Z","tags":[],"pid":18203,"method":"get","statusCode":404,"req":{"url":"/elasticsearch/dsp-log-ec173_2017-10-24/mapping/field/*?=1508876584172&ignore_unavailable=false&allow_no_indices=false&include_defaults=true","method":"get","headers":{"host":"kibana.x.x.x.x.com","x-real-ip":"x.x.x.x","x-forwarded-for":"x.x.x.x","x-forwarded-proto":"http","connection":"close","accept":"application/json, text/plain, /","kbn-version":"5.3.1","user-agent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/60.0.3112.78 Chrome/60.0.3112.78 Safari/537.36","referer":"http://kibana.x.x.x.x.com/app/kibana","accept-encoding":"gzip, deflate","accept-language":"en-US,en;q=0.8"},"remoteAddress":"127.0.0.1","userAgent":"127.0.0.1","referer":"http://kibana.x.x.x.x.com/app/kibana"},"res":{"statusCode":404,"responseTime":11,"contentLength":9},"message":"GET /elasticsearch/dsp-log-ec173_2017-10-24/mapping/field/*?=1508876584172&ignore_unavailable=false&allow_no_indices=false&include_defaults=true 404 11ms - 9.0B"}