[CI] MixedClusterClientYamlTestSuiteIT class failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #11505 / 9.0.8_bwc
• elasticsearch-periodic #11502 / 9.0.8_bwc
• elasticsearch-periodic #11498 / 9.0.8_bwc
• elasticsearch-periodic #11493 / 9.0.8_bwc
• elasticsearch-pull-request #105952 / 9.0.8_bwc
• elasticsearch-periodic #11489 / 9.0.8_bwc
• elasticsearch-pull-request #105656 / 9.0.8_bwc
• elasticsearch-pull-request #105619 / 9.0.8_bwc
• elasticsearch-periodic #11483 / 9.0.8_bwc
• elasticsearch-periodic #11479 / 9.0.8_bwc

Reproduction Line:

./gradlew ":qa:mixed-cluster:v9.0.8#mixedClusterTest" -Dtests.class="org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT" -Dtests.method="test {p0=search/330_fetch_fields/Test with subobjects: auto}" -Dtests.seed=B3255F79159EEDC5 -Dtests.bwc=true -Dtests.locale=ko-KR -Dtests.timezone=Europe/Istanbul -Druntime.java=25

Applicable branches:
9.1

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Failure at [search/330_fetch_fields:1131]: expected [2xx] status code but api [indices.create] returned [400 Bad Request] [{"error":{"root_cause":[{"type":"parse_exception","reason":"unknown subobjects value: auto","stack_trace":"org.elasticsearch.ElasticsearchParseException: unknown subobjects value: auto\n\tat org.elasticsearch.index.mapper.ObjectMapper$Subobjects.from(ObjectMapper.java:87)\n\tat org.elasticsearch.index.mapper.ObjectMapper$TypeParser.parseSubobjects(ObjectMapper.java:349)\n\tat org.elasticsearch.index.mapper.RootObjectMapper.parse(RootObjectMapper.java:452)\n\tat org.elasticsearch.index.mapper.MappingParser.parse(MappingParser.java:125)\n\tat org.elasticsearch.index.mapper.MapperService.parseMapping(MapperService.java:631)\n\tat org.elasticsearch.index.mapper.MapperService.doMerge(MapperService.java:580)\n\tat org.elasticsearch.index.mapper.MapperService.merge(MapperService.java:464)\n\tat org.elasticsearch.cluster.metadata.MetadataCreateInd
[truncated]

Issue Reasons:

• [9.1] 13 failures in class org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT (12.1% fail rate in 107 executions)
• [9.1] 13 failures in step 9.0.8_bwc (92.9% fail rate in 14 executions)
• [9.1] 9 failures in pipeline elasticsearch-periodic (100.0% fail rate in 9 executions)
• [9.1] 4 failures in pipeline elasticsearch-pull-request (12.1% fail rate in 33 executions)

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

[elasticsearchmachine]

Pinging @elastic/es-delivery (Team:Delivery)