This is related to JGRP-918.

The UUID class keeps a static cache of logical names, which is shared by all the clusters running in the same JVM. When TP receives a VIEW_CHANGED event, it calls UUID.retainAll(members), which marks all the addresses on other clusters for removal. If there are enough members to exceed the logical names cache capacity (500 by default), some of those members will be actually removed from the logical names cache and their addresses will be printed as UUIDs.