Document centric external version conflict not returning 409

[Deepu]

Hi Team,

I am using Solr document centric external version configuration to control
concurrent updates.
Followed sample configuration given in below github path.
https://github.com/apache/lucene-solr/blob/master/solr/core/src/test-files/solr/collection1/conf/solrconfig-externalversionconstraint.xml

Document not getting updated if the new document's external version is less
than the existing one, but it is not giving response status code as 409,
still getting status=0 in update response, need to configure anything else
to get status=409 in response.

<updateRequestProcessorChain name="external-version-constraint">
  <processor class="solr.DefaultValueUpdateProcessorFactory">
    <str name="fieldName">live_b</str>
    <bool name="value">true</bool>
  </processor>

  <processor class="solr.DocBasedVersionConstraintsProcessorFactory">
    <str name="versionField">_external_version_</str>
    <str name="deleteVersionParam">_external_version_</str>
  </processor>

  <processor class="solr.DefaultValueUpdateProcessorFactory">
    <str name="fieldName">live_b</str>
    <bool name="value">false</bool>
  </processor>

  <processor class="solr.TimestampUpdateProcessorFactory">
    <str name="fieldName">update_timestamp_tdt</str>
  </processor>

  <processor class="solr.LogUpdateProcessorFactory" />
  <processor class="solr.RunUpdateProcessorFactory" />
</updateRequestProcessorChain>


I am using Solr version : 8.6.1 and Solrj version : 8.4.0

Thanks,
Deepu