TeamCity - SVN and Labelling: How to do it correctly?

Question

I've read all the TeamCity, SVN and labeling questions in S.O. but none seams to apply to my specific problem.

Here we have the following structure on the SVN:

svn://server/root
              /projectA
                 /trunk
                 /tags
              /projectB
                 /trunk
                 /tags

On the TeamCity I've configured a SVN root for the project A like this:

svn://server/root/ProjectA/trunk

And the build process works like a charm.

However now I want to add labeling, but even setting the labeling rules as specified in the documentation or any other setting I know of, as for my latest try:

/ProjectA/trunk=>/ProjectA/tags

I get the following error:

jetbrains.buildServer.vcs.VcsException: Labeling the path 'ProjectA/trunk' to 'ProjectA/tags/build-24' has failed with the error: svn: CHECKOUT of '/svn/root/!svn/ver/5792/ProjectA/tags': 403 Forbidden (https://server:8443)
  at jetbrains.buildServer.buildTriggers.vcs.svn.SvnSupport.throwLabelingError(SvnSupport.java:430)
  at jetbrains.buildServer.buildTriggers.vcs.svn.SvnSupport.label(SvnSupport.java:418)
  at jetbrains.buildServer.vcs.impl.VcsLabeler.setLabel(VcsLabeler.java:45)
  at jetbrains.buildServer.vcs.impl.VcsLabeler.access$400(VcsLabeler.java:64)
  at jetbrains.buildServer.vcs.impl.VcsLabeler$3$1.run(VcsLabeler.java:4)
  at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
  at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
  at java.util.concurrent.FutureTask.run(Unknown Source)
  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
  at java.lang.Thread.run(Unknown Source)
Caused by: org.tmatesoft.svn.core.SVNAuthenticationException: svn: CHECKOUT of '/svn/root/!svn/ver/5792/ProjectA/tags': 403 Forbidden (https://server:8443)
  at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:62)
  at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:51)
  at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:623)
  at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:274)
  at org.tmatesoft.svn.core.internal.io.dav.http.HTTPConnection.request(HTTPConnection.java:262)
  at org.tmatesoft.svn.core.internal.io.dav.DAVConnection.doCheckout(DAVConnection.java:452)
  at org.tmatesoft.svn.core.internal.io.dav.DAVCommitEditor.checkoutResource(DAVCommitEditor.java:468)
  at org.tmatesoft.svn.core.internal.io.dav.DAVCommitEditor.addDir(DAVCommitEditor.java:136)
  at jetbrains.buildServer.buildTriggers.vcs.svn.SvnCopyHelper$CopyCommitPathHandler.handleCommitPath(SvnCopyHelper.java:138)
  at org.tmatesoft.svn.core.internal.wc.SVNCommitUtil.driveCommitEditor(SVNCommitUtil.java:139)
  at jetbrains.buildServer.buildTriggers.vcs.svn.SvnCopyHelper.doCopy(SvnCopyHelper.java:102)
  at jetbrains.buildServer.buildTriggers.vcs.svn.SvnConnection.label(SvnConnection.java:861)
  at jetbrains.buildServer.buildTriggers.vcs.svn.SvnSupport.label(SvnSupport.java:416)

Does anyone has any reason why this happen, or how can I set up this correctly?

In time: The user accessing the SVN does the checkout correctly as the TeamCity is configured to clean the checkout folder before every build.