javadoc errors

We are having the following problem generating javadocs using

mvn javadoc:aggregate -DskipTest=true -P site,\!build-ui

[ERROR] Exit code: 1 - javadoc: warning - Multiple sources of package
comments found for package "org.osgi.framework"

[ERROR] javadoc: warning - Multiple sources of package comments found for
package "org.apache.commons.collections"

[ERROR] javadoc: warning - Multiple sources of package comments found for
package "org.acplt.oncrpc"

[ERROR] javadoc: warning - Multiple sources of package comments found for
package "org.apache.commons.beanutils"

[ERROR]
com/googlecode/concurrentlinkedhashmap/ConcurrentLinkedHashMap.class(com/googlecode/concurrentlinkedhashmap:ConcurrentLinkedHashMap.class):
warning: Cannot find annotation method 'value()' in type
'javax.annotation.concurrent.GuardedBy': class file for
javax.annotation.concurrent.GuardedBy not found

[ERROR]
com/googlecode/concurrentlinkedhashmap/ConcurrentLinkedHashMap.class(com/googlecode/concurrentlinkedhashmap:ConcurrentLinkedHashMap.class):
warning: Cannot find annotation method 'value()' in type
'javax.annotation.concurrent.GuardedBy'

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But I've had no luck at all adding <excludePackageNames> to our top-level
pom.xml, e.g..

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-javadoc-plugin</artifactId>

<version>${maven-javadoc-plugin.version}</version>

<configuration>

<excludePackageNames>org.osgi.framework.*,com.googlecode.*</excludePackageNames>

</configuration>

<reportSets>

<reportSet>

<id>html</id>

<reports>

<report>javadoc</report>

</reports>

</reportSet>

</reportSets>

</plugin>

Any troubleshooting tips would be appreciated. Thanks.