Hi
Off the top of my head, could it be a collision between giving column names in your filter and having autodetect_column_names => true?
If you keep it to false you can give the filter your own column names and use more than 1 worker.
You can check the documentation for the csv filter here: https://www.elastic.co/guide/en/logstash/current/plugins-filters-csv.html
Just a thought.