[CI] RcsCcsCommonYamlTestSuiteIT test {p0=search.vectors/42_knn_search_int4_flat/KNN Vector similarity search only} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #6137 / oraclelinux-8_platform-support-unix
• elasticsearch-periodic-platform-support #6130 / rocky-8_platform-support-unix
• elasticsearch-periodic-platform-support #6109 / ubuntu-2204_platform-support-unix
• elasticsearch-periodic #6113 / openjdk21_checkpart1_java-matrix
• elasticsearch-pull-request #54371 / part-1

Reproduction Line:

./gradlew ":qa:ccs-common-rest:yamlRestTest" --tests "org.elasticsearch.test.rest.yaml.RcsCcsCommonYamlTestSuiteIT" -Dtests.method="test {p0=search.vectors/42_knn_search_int4_flat/KNN Vector similarity search only}" -Dtests.seed=5AEE056EF2C70E58 -Dtests.locale=es-PE -Dtests.timezone=SystemV/HST10 -Druntime.java=23

Applicable branches:
9.0

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Failure at [search.vectors/42_knn_search_int4_flat:209]: field [hits.hits] doesn't have length [1]
Expected: <1>
     but: was <0>

Issue Reasons:

• [9.0] 5 failures in test test {p0=search.vectors/42_knn_search_int4_flat/KNN Vector similarity search only} (2.6% fail rate in 191 executions)
• [9.0] 3 failures in pipeline elasticsearch-periodic-platform-support (42.9% fail rate in 7 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

This has been muted on branch main

Mute Reasons:

• [main] 2 failures in test test {p0=search.vectors/42_knn_search_int4_flat/KNN Vector similarity search only} (0.3% fail rate in 579 executions)

Build Scans:

• elasticsearch-periodic-platform-support #6093 / rhel-8_platform-support-unix
• elasticsearch-pull-request #53533 / part-1-fips

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)

[elasticsearchmachine]

This has been muted on branch 9.0

Mute Reasons:

• [9.0] 4 failures in test test {p0=search.vectors/42_knn_search_int4_flat/KNN Vector similarity search only} (2.4% fail rate in 166 executions)
• [9.0] 2 failures in pipeline elasticsearch-periodic-platform-support (33.3% fail rate in 6 executions)

Build Scans:

• elasticsearch-periodic-platform-support #6130 / rocky-8_platform-support-unix
• elasticsearch-periodic-platform-support #6109 / ubuntu-2204_platform-support-unix
• elasticsearch-periodic #6113 / openjdk21_checkpart1_java-matrix
• elasticsearch-pull-request #54371 / part-1