I have, albeit inadvertently managed to recreate the issue, which caused
the errorError: JMX connector server communication error:
service:jmx:rmi://:8463The message was slightly misleading,
as the problem seems to be that port 8463 was still listening, when the
AEM instance tried to restart after the backup process had failed, due
to a full file system.Having cleared down the file system, we have not
seen a re-occurrence of the issue.