Keycloak 15.0.2 docker image issue

Please see that post: How to use the Keycloak jboss/keycloak:15.0.2 docker image? - Stack Overflow
I would like to know what I am doing wrong and why a simple docker run of the jboss/keycloak:15.0.2 does not work?

If your v11 and v15 containers are on the same network, this is the kind of error that you will see because of incompatibilities between versions of infinispan.

Thank you.
I noticed that stopping the container running the V11 sloved the issue. I would like to know why? The goal of containers is isolation, so why a container impacts another one?

When Keycloak starts, it starts Infinispan discovery for other instances of the distributed cache. By default, it uses multicast over the network to find other instances so that it can share/replicate the cache. Unless your containers are running on isolated networks, this will happen.