We were running SonarQube 9.9.3 ee and in my absence a colleague tried to update to 2025.4 not knowing 2025.1 must not be skipped.
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jdk.internal.loader.ClassLoaders$AppClassLoader@5bc2b487-org.sonar.server.platform.DatabaseServerCompatibility': The version of SonarQube you are trying to upgrade from is too old. Please upgrade to the 2025.1 Long-Term Active version first.
Next step was to create a 2025.1 ee image and try to deploy that.
This fails too now because some parts of the upgrade to 2025.4 seem to have worked:
ERROR es[][o.e.b.Elasticsearch] fatal exception while booting Elasticsearch
java.lang.IllegalStateException: cannot downgrade a node from version [8.16.3] to version [8.16.1]
at org.elasticsearch.env.NodeMetadata.verifyUpgradeToCurrentVersion(NodeMetadata.java:135) ~[elasticsearch-8.16.1.jar:?]
Could it possibly help to delete $SONARQUBE_HOME/data/es8?
Any other ideas?