Hi @Ferenc ,
there were some other users hitting this on AKS ( thread ) with 8.6. this is probably related to a limitation of the Azure File Storage (feature request). there is a workaround in the thread that i linked you.
As for the issues you are facing with 8.4. we changed the way we are shipping our language analyzers with 8.5 so with 8.4 you have probably overwritten the /opt/sonarqube/extensions directory inside the container with an empty volume. you need to download the analyzer plugins you need into this empty directory manually or copy them from another container that is instantiated with the 8.4 docker image into the volume.
hope that helps