[CI] ClassificationIT testWithOnlyTrainingRowsAndTrainingPercentIsFifty_DependentVariableIsTextAndKeyword failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #6354 / openjdk17_checkpart4_java-matrix
• elasticsearch-periodic #6249 / openjdk17_checkpart4_java-fips-matrix

Reproduction Line:

./gradlew ":x-pack:plugin:ml:qa:native-multi-node-tests:javaRestTest" --tests "org.elasticsearch.xpack.ml.integration.ClassificationIT.testWithOnlyTrainingRowsAndTrainingPercentIsFifty_DependentVariableIsTextAndKeyword" -Dtests.seed=1EA69F38DA4EE0D0 -Dtests.locale=vi -Dtests.timezone=Asia/Pontianak -Druntime.java=17

Applicable branches:
8.x

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Stats were: {"id":"classification_training_percent_is_50_text_and_keyword","state":"started","progress":[{"phase":"reindexing","progress_percent":100},{"phase":"loading_data","progress_percent":100},{"phase":"feature_selection","progress_percent":100},{"phase":"coarse_parameter_search","progress_percent":89},{"phase":"fine_tuning_parameters","progress_percent":0},{"phase":"final_training","progress_percent":0},{"phase":"writing_results","progress_percent":0},{"phase":"inference","progress_percent":0}],"data_counts":{"training_docs_count":150,"test_docs_count":0,"skipped_docs_count":0},"memory_usage":{"timestamp":1739341465564,"peak_usage_bytes":19083,"status":"ok"},"node":{"id":"XGdfcRJVTV-veWv0qWOigw","name":"javaRestTest-1","ephemeral_id":"NXCBQKgrQPOlY0KfN7VTIw","transport_address":"127.0.0.1:33783","attributes":{"testattr":"test","xpack.installed":"true","transform.config_version":"10.0.0","ml.config_version":"12.0.0","ml.max_jvm_size":"536870912","ml.allo
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Issue Reasons:

• [8.x] 2 failures in test testWithOnlyTrainingRowsAndTrainingPercentIsFifty_DependentVariableIsTextAndKeyword (0.3% fail rate in 634 executions)
• [8.x] 2 failures in pipeline elasticsearch-periodic (12.5% fail rate in 16 executions)

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

[elasticsearchmachine]

Pinging @elastic/ml-core (Team:ML)

[elasticsearchmachine]

This has been muted on branch 8.18

Mute Reasons:

• [8.18] 3 failures in test testWithOnlyTrainingRowsAndTrainingPercentIsFifty_DependentVariableIsTextAndKeyword (1.7% fail rate in 178 executions)

Build Scans:

• elasticsearch-periodic #6261 / openjdk17_checkpart4_java-matrix
• elasticsearch-pull-request #55525 / part-4
• elasticsearch-intake #17443 / part4