What the WARN message "Server locator is closed (maybe it was garbage collected): java.lang.IllegalStateException: Server locator is closed (maybe it was garbage collected)" means?

Issue

The broker is displaying the WARN message before it shutdown.

WARN  [org.apache.activemq.artemis.utils.actors.OrderedExecutor] Server locator is closed (maybe it was garbage collected): java.lang.IllegalStateException: Server locator is closed (maybe it was garbage collected)
    at org.apache.activemq.artemis.core.client.impl.ServerLocatorImpl.assertOpen(ServerLocatorImpl.java:....) 
....

or this ERROR :

ERROR [org.apache.activemq.artemis.core.client] AMQ214015: Failed to execute connection life cycle listener: java.util.concurrent.RejectedExecutionException: Task org.apache.activemq.artemis.utils.actors.ProcessorBase$$Lambda$33/... rejected from java.util.concurrent.ThreadPoolExecutor@...[Shutting down, pool size = 5, active threa
ds = 0, queued tasks = 0, completed tasks = ...]
        at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:...)
        at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:...) [rt.jar:...]