Warning "x of y shards failed"

What should I do after getting the warning “x of y shards failed” in Kibana?

If the user wants to see all index data and does not want to see the warning message, then add the required field mappings in templates and for older indexes.

To add field mapping in the Txnstore index, run one ‘PUT’ command in Txnstore.

Refer Kibana Reporting