[CI] ThreadPoolMergeExecutorServiceDiskSpaceTests testAvailableDiskSpaceMonitorWhenFileSystemStatErrors failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #8800 / amazonlinux-2_platform-support-aws
• elasticsearch-periodic-platform-support #8788 / oraclelinux-7_platform-support-unix
• elasticsearch-periodic #8755 / openjdk22_checkpart1_java-matrix
• elasticsearch-periodic #8749 / openjdk17_checkpart1_java-fips-matrix
• elasticsearch-periodic-platform-support #8746 / windows-2025_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #8716 / rocky-8_platform-support-unix
• elasticsearch-pull-request #74958 / part-1

Reproduction Line:

./gradlew ":server:test" --tests "org.elasticsearch.index.engine.ThreadPoolMergeExecutorServiceDiskSpaceTests.testAvailableDiskSpaceMonitorWhenFileSystemStatErrors" -Dtests.seed=66FC033338F50A37 -Dtests.locale=ja-JP -Dtests.timezone=Australia/LHI -Druntime.java=24

Applicable branches:
8.19

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: 
Expected: is <3>
     but: was <2>

Issue Reasons:

• [8.19] 7 failures in test testAvailableDiskSpaceMonitorWhenFileSystemStatErrors (1.1% fail rate in 651 executions)
• [8.19] 4 failures in pipeline elasticsearch-periodic-platform-support (25.0% fail rate in 16 executions)
• [8.19] 2 failures in pipeline elasticsearch-periodic (13.3% fail rate in 15 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] 3 failures in test testAvailableDiskSpaceMonitorWhenFileSystemStatErrors (3.6% fail rate in 84 executions)
• [main] 2 failures in step part-1 (8.7% fail rate in 23 executions)
• [main] 2 failures in pipeline elasticsearch-pull-request (8.7% fail rate in 23 executions)

Build Scans:

• elasticsearch-periodic-platform-support #8676 / almalinux-8-aarch64_checkpart1_platform-support-arm
• elasticsearch-pull-request #74614 / part-1
• elasticsearch-pull-request #74583 / part-1

[elasticsearchmachine]

Pinging @elastic/es-distributed-indexing (Team:Distributed Indexing)