[CI] KeywordSyntheticSourceNativeArrayIntegrationTests testSynthesizeEmptyArray failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #6668 / release-tests
• elasticsearch-periodic #6662 / release-tests
• elasticsearch-periodic #6655 / release-tests
• elasticsearch-periodic #6648 / release-tests
• elasticsearch-periodic #6529 / release-tests

Reproduction Line:

./gradlew ":server:test" --tests "org.elasticsearch.index.mapper.KeywordSyntheticSourceNativeArrayIntegrationTests.testSynthesizeArray" -Dtests.seed=C245918E159AA8E9 -Dbuild.snapshot=false -Dtests.jvm.argline="-Dbuild.snapshot=false" -Dlicense.key=x-pack/license-tools/src/test/resources/public.key -Dtests.locale=th-Thai-TH -Dtests.timezone=America/Atka -Druntime.java=23

Applicable branches:
8.x

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: 
Expected: iterable with items ["_id", "_ignored_source"] in any order
     but: not matched: "_recovery_source"

Issue Reasons:

• [8.x] 4 consecutive failures in step release-tests
• [8.x] 5 failures in test testSynthesizeEmptyArray (0.5% fail rate in 927 executions)
• [8.x] 5 failures in step release-tests (27.8% fail rate in 18 executions)
• [8.x] 5 failures in pipeline elasticsearch-periodic (23.8% fail rate in 21 executions)

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

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)