Infinite loop of retryable error code=>400

Hello,
We're using filebeat that sends data to logstash, suddenly we started receiving

Encountered a retryable error. Will Retry with exponential backoff  {:code=>400, :url=>"http://localhost:9200/_bulk"}

From filebeat's side it sends the relevant logs without any errors and it looks like the maximum size of a log sent by it is 23kb so I don't think it a log size problem.

what can cause this?

What is the complete error message? What does elasticsearch log when this happens?


this is the full error, as you can see it just repeats itself over and over.
about the elastic: seems like it doesn't log anything about it... there are only logs from received metrics from the metricbeat