P2 Update Site Proxy / Item not found for request because of wrong name

When creating a P2 Update site proxy (for Apache Directory Studio 2.X http://directory.apache.org/studio/update/2.x/, see attached screenshot for complete configuration), some components cannot be downloaded, as it seems the versions of the jars being looked for are incorrect.

For example the task searches for a "plugins/org.apache.commons.codec_1.6.jar" but it should be looking for "plugins/org.apache.commons.codec_1.6.0.jar", judging from the site.xml file. The full log and site.xml files can be found as attachments.

It should be noted that I can install the directory studio without problem when using the apache update site, but it is not possible when going through the proxy update site.