How can I troubleshoot 'json parse error' failures when using the Logstash 'json' codec?

Start by examining the Logstash logs for specific error messages related to the parse failure. Check the input data for syntax errors using a JSON validator. Verify that the data is properly encoded as UTF-8. Consider using the 'mutate' filter to remove or replace problematic characters before parsing. Reduce the complexity of the JSON structure to isolate the problem and identify the offending parts.