SetLoopbackModeIPv4 FAILED in Test_openjdk11_hs_extended.openjdk_s390x_linux

**Failing Test Info**
Test Name: java/net/MulticastSocket/SetLoopbackModeIPv4.java
Test Duration: 6.5 seconds
Machine it fails on: [test-marist-ubuntu2404-s390x-1](https://ci.adoptium.net/computer/test-marist-ubuntu2404-s390x-1)
Machines it passes on (if intermittent): [test-docker-ubuntu2404-s390x-1](https://ci.adoptium.net/computer/test-docker-ubuntu2404-s390x-1) [test-docker-sles15-s390x-1](https://ci.adoptium.net/computer/test-docker-sles15-s390x-1)
Confirmed: Can passes and fail on the same machine. Grinder passes, but named job can fail.

**Jenkins Test Job Info**
Jenkins Test Job Name: Test_openjdk11_hs_extended.openjdk_s390x_linux_testList_6
Jenkins Test Job URL: https://ci.adoptium.net/job/Test_openjdk11_hs_extended.openjdk_s390x_linux_testList_6/35/
TRSS link for the build (if available): https://trss.adoptium.net/allTestsInfo?buildId=698939ca928502006ed0cc13&limit=1

**Deep History Link from TRSS (if available)**

https://trss.adoptium.net/deepHistory?testId=69893d6d928502006ed0f057

** Rerun in Grinder Link (if available) or Steps to Reproduce**

[Grinder link.](https://ci.adoptium.net/job/Grinder/parambuild/?SDK_RESOURCE=upstream&TARGET=jdk_custom&BASE_DOCKER_REGISTRY_CREDENTIAL_ID=&TEST_FLAG=&UPSTREAM_TEST_JOB_NAME=Test_openjdk11_hs_extended.openjdk_s390x_linux&DOCKER_REQUIRED=false&ACTIVE_NODE_TIMEOUT=5&VENDOR_TEST_DIRS=&EXTRA_DOCKER_ARGS=&TKG_OWNER_BRANCH=adoptium%3Amaster&OPENJ9_SYSTEMTEST_OWNER_BRANCH=eclipse%3Amaster&PLATFORM=s390x_linux&GENERATE_JOBS=true&KEEP_REPORTDIR=true&PERSONAL_BUILD=false&DOCKER_REGISTRY_DIR=&RERUN_ITERATIONS=0&ADOPTOPENJDK_REPO=https%3A%2F%2Fgithub.com%2Fadoptium%2Faqa-tests.git&SETUP_JCK_RUN=false&DOCKER_REGISTRY_URL_CREDENTIAL_ID=&LABEL=&EXTRA_OPTIONS=&CUSTOMIZED_SDK_URL=&BUILD_IDENTIFIER=&JENKINS_KEY=&ADOPTOPENJDK_BRANCH=master&LIGHT_WEIGHT_CHECKOUT=false&USE_JRE=false&ARTIFACTORY_SERVER=&KEEP_WORKSPACE=false&USER_CREDENTIALS_ID=&JDK_VERSION=11&DOCKER_REGISTRY_URL=&ITERATIONS=1&VENDOR_TEST_REPOS=&JDK_REPO=https%3A%2F%2Fgithub.com%2Fadoptium%2Fjdk11u&JCK_GIT_BRANCH=master&OPENJ9_BRANCH=master&OPENJ9_SHA=&JCK_GIT_REPO=&VENDOR_TEST_BRANCHES=&UPSTREAM_JOB_NAME=build-scripts%2Fjobs%2Fjdk11u%2Fjdk11u-linux-s390x-temurin&OPENJ9_REPO=https%3A%2F%2Fgithub.com%2Feclipse-openj9%2Fopenj9.git&CLOUD_PROVIDER=&CUSTOM_TARGET=java%2Fnet%2FMulticastSocket%2FSetLoopbackModeIPv4.java&VENDOR_TEST_SHAS=&JDK_BRANCH=jdk-11.0.31%2B1_adopt&LABEL_ADDITION=&ARTIFACTORY_REPO=&ARTIFACTORY_ROOT_DIR=&UPSTREAM_TEST_JOB_NUMBER=232&DOCKERIMAGE_TAG=&TEST_TIME=&JDK_IMPL=hotspot&SSH_AGENT_CREDENTIAL=&AUTO_DETECT=true&SLACK_CHANNEL=aqavit-bot&DYNAMIC_COMPILE=false&RELATED_NODES=&ADOPTOPENJDK_SYSTEMTEST_OWNER_BRANCH=adoptium%3Amaster&APPLICATION_OPTIONS=&CUSTOMIZED_SDK_URL_CREDENTIAL_ID=eclipse_temurin_bot_email_and_token&ARCHIVE_TEST_RESULTS=false&NUM_MACHINES=&OPENJDK_SHA=&TRSS_URL=&RERUN_FAILURE=false&USE_TESTENV_PROPERTIES=false&BUILD_LIST=openjdk&ADDITIONAL_ARTIFACTS_REQUIRED=&UPSTREAM_JOB_NUMBER=388&STF_OWNER_BRANCH=adoptium%3Amaster&TIME_LIMIT=25&JVM_OPTIONS=&PARALLEL=None)

**Java Version output (from console output)**

```
23:35:21 openjdk version "11.0.31-beta" 2026-04-21
23:35:21 OpenJDK Runtime Environment Temurin-11.0.31+1-202602062103 (build 11.0.31-beta+1-ea)
23:35:21 OpenJDK 64-Bit Server VM Temurin-11.0.31+1-202602062103 (build 11.0.31-beta+1-ea, mixed mode)
```

**Relevant Console Output (showing exceptions/errors/crashes)**

```
01:03:00 STDOUT:
01:03:00
01:03:00 Test will use multicast group: /224.80.80.80
01:03:00
01:03:00 ******************
01:03:00
01:03:00 Loopback mode is disabled.
01:03:00 Packet not received - correct.
01:03:00
01:03:00 ******************
01:03:00
01:03:00 Loopback mode is enabled.
01:03:00 Packet not received (packet excepted as loopback is enabled)
01:03:00
01:03:00 ******************
01:03:00
01:03:00 STDERR:
01:03:00 java.lang.RuntimeException: Test failed
01:03:00 at SetLoopbackMode.main(SetLoopbackMode.java:133)
01:03:00 at SetLoopbackModeIPv4.main(SetLoopbackModeIPv4.java:41)
01:03:00 at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
01:03:00 at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
01:03:00 at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
01:03:00 at java.base/java.lang.reflect.Method.invoke(Method.java:566)
01:03:00 at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
01:03:00 at java.base/java.lang.Thread.run(Thread.java:829)
```

**Attach or link to relevant artifacts**

[SetLoopbackModeIPv4.jtr.xml](https://github.com/user-attachments/files/25210242/SetLoopbackModeIPv4.jtr.xml)

[SetLoopbackModeIPv4.jtr.txt](https://github.com/user-attachments/files/25210244/SetLoopbackModeIPv4.jtr.txt)

Related issues: https://github.com/adoptium/infrastructure/issues/3189 maybe. Will retest when this is resolved, or visa versa.

Start with java/net/MulticastSocket/SetLoopbackModeIPv4.java and SetLoopbackMode.java:133, then review the attached JTR artifacts and compare the linked passing and failing machine results. Reproduce using the provided Grinder link and check related infrastructure issue 3189. Done means the intermittent failure has an identified cause and an agreed test or infrastructure resolution.

Written by the indexing model from the issue text.