CNF and JGRP000012 occurred after migration from EAP 6.4 to 7.3 with JBoss Server Migration Tool

Issue

After migrating EAP configuration from 6.4 to 7.3 with JBoss Server Migration Tool, clustered EAP shows JGRP000012 sometimes.

WARN  [org.jgroups.protocols.UDP] (thread-13,ee-ejb,jboss_node1) JGRP000012: discarded message from different cluster ee-web (our cluster is ee-ejb). Sender was jboss_node1 (received 25 identical messages from jboss_node1 in the last 61237 ms)
WARN  [org.jgroups.protocols.UDP] (thread-8,ee-web,jboss_node1) JGRP000012: discarded message from different cluster ee-ejb (our cluster is ee-web). Sender was jboss_node1 (received 25 identical messages from jboss_node1 in the last 61218 ms)