Empty MetaModel when using EclipseLink 2.7.4 - eclipselink

Question

My application has a composite persistence unit mainPU which contains 2 members (queryPU and entityPU). When using Criteria API in EclipseLink 2.5, it did not have any problem. However, when upgrading to EclipseLink 2.7, it got error "No [EntityType] was found for the key class [XXX] in the Metamodel" where XXX is the class defined in entityPU
I have some observation regarding the issue:
This problem only occurred when using Criteria API, and there is no
problem when using JPQL.
By default, my application load the mainPU. If I try to get the meta model, it always return empty list. If I explicitly load the
EntityManagerFactory with entityPU in a DAO, then it can load the full list of EntityType, and the problem gone!
EntityManagerFactory factory = Persistence.createEntityManagerFactory("entityPU");
Metamodel m2 = factory.getMetamodel(); //m2 return a list of EntityType!
Is there any wrong configuration in my application for the EclipseLink 2.7?
Below show the persistence.xml
mainPU
<?xml version="1.0" encoding="UTF-8"?>
<persistence
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="mainPU" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>java:jboss/datasources/appds</jta-data-source>
<jar-file>icms-entity-lib-0.2.9.544.jar</jar-file>
<jar-file>../icmshrnmc-ejb.jar</jar-file>
<properties>
<property name="jboss.entity.manager.jndi.name" value="java:jboss/persistence/mainPU" />
<property name="eclipselink.target-database"
value="org.eclipse.persistence.platform.database.oracle.Oracle11Platform" />
<property name="eclipselink.target-server" value="JBoss" />
<property name="eclipselink.composite-unit" value="true" />
<property name="eclipselink.session.customizer"
value="x.y.ejb.dao.entity.DefaultEntityInterceptor" />
<property name="eclipselink.logging.level" value="ALL" />
<property name="eclipselink.deploy-on-startup" value="true"/>
</properties>
</persistence-unit>
queryPU
<?xml version="1.0" encoding="UTF-8"?>
<persistence
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="queryPU" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>java:jboss/datasources/appds</jta-data-source>
<mapping-file>x/y/icmshrnmc/model/common/dao/namedquery/HrnNat.orm.xml</mapping-file>
...
...
...
<properties>
<property name="eclipselink.composite-unit-member" value="true" />
</properties>
</persistence-unit>
entityPU
<?xml version="1.0" encoding="UTF-8"?>
<persistence
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="entityPU" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>java:jboss/datasources/appds</jta-data-source>
<non-jta-data-source>java:jboss/datasources/appds</non-jta-data-source>
<mapping-file>x/y/fmk/model/application/dao/entity/AuditEntity.orm.xml</mapping-file>
...
...
...
<shared-cache-mode>NONE</shared-cache-mode>
<properties>
<property name="eclipselink.jdbc.sequence-connection-pool" value="true" />
<property name="eclipselink.jdbc.sequence-connection-pool.non-jta-data-source" value="java:jboss/datasources/fmkseqds" />
</properties>