Failure during space import

Rp Subhub

1. Install and setup Confluence 5.4.4
2. Add 2 users
3. Create space, add page
4. Log in as user1 and add to favourites a page from this space
5. Log in as user2 and add to favourites the same page
6. Export space to XML
7. Install and setup Confluence 5.4.4 (to start clean again)
8. Add 2 users
9. Import space from xml.zip
10. Get error "Import failed. Check your server logs for more information. duplicate key: class=class com.atlassian.confluence.labels.Label"
11. Go to dashboard
12. Space is there
13. Log in as user1
14. Observe that page you favourited is listed two times under your favourite pages
15. Log in as user2
16. Observe that page you favourited is not listed at all under your favourite pages

In the log file:

2014-04-24 20:10:26,371 ERROR [Long running task: Importing data] [confluence.importexport.actions.ImportLongRunningTask] runInternal Failure during import
 -- referer: http://localhost:1990/confluence/admin/backup.action | url: /confluence/admin/restore-local-file.action | userName: admin | action: restore-local-file
java.lang.IllegalArgumentException: duplicate key: class=class com.atlassian.confluence.labels.Label,id=1212417,<null>
        at com.google.common.base.Preconditions.checkArgument(Preconditions.java:115)
        at com.google.common.collect.RegularImmutableMap.<init>(RegularImmutableMap.java:72)
        at com.google.common.collect.ImmutableMap$Builder.fromEntryList(ImmutableMap.java:221)
        at com.google.common.collect.ImmutableMap$Builder.build(ImmutableMap.java:207)
        at com.google.common.collect.RegularImmutableBiMap.<init>(RegularImmutableBiMap.java:39)
        at com.google.common.collect.ImmutableBiMap$Builder.build(ImmutableBiMap.java:176)
        at com.atlassian.confluence.importexport.DefaultImmutableImportProcessorSummary.newInstance(DefaultImmutableImportProcessorSummary.java:99)
        at com.atlassian.confluence.importexport.DefaultImportExportManager.performImport(DefaultImportExportManager.java:73)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
        at $Proxy77.performImport(Unknown Source)
        at com.atlassian.confluence.importexport.actions.ImportLongRunningTask.runInternal(ImportLongRunningTask.java:88)
        at com.atlassian.confluence.util.longrunning.ConfluenceAbstractLongRunningTask.run(ConfluenceAbstractLongRunningTask.java:26)
        at com.atlassian.confluence.util.longrunning.ManagedTask.run(ManagedTask.java:35)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662)

There are duplicate entries in the CONTENT_LABEL table (on labelid + contentid).

Questions:

1. Is this error harmless besides messing with favourites?
2. Is it a known issue?

Rp Subhub

After further investigation I found out it depends on order of elements in the export XML file. Order is somewhat random. If you're unlucky you end up with objects of class ConfluenceUserImpl being after objects of class Label. Space import fails in that case (if you have a page favourited by two users).