Infinite loop of retryable error code=>400

[maxonage (Max)]

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?

[Badger]

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

[maxonage (Max)]

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