...

The problem is related to the communication with your BO server and the timeout settings. 

Solution 1 (timeout increase)

There is only a workaround we can currently offer by extending your timeout-time.

...

  <system.serviceModel>
    <bindings>
      <basicHttpBinding>
        <binding name="DpBoWebServiceClient" sendTimeout="00:10:00">
        </binding>
      </basicHttpBinding>
    </bindings>
  </system.serviceModel>

Solution 2 (stabilize folder retrieval)

If the "timeout-value-increase" still does not work, you can switch to the slower, but more stable way of calling the folder structure:

1. Go to the folder ..\DocuPerformer\Core\Main
2. Find the file DocuPerformer.exe.config
3. Open this file DocuPerformer.exe.config with a text editor
4. Jump to line 236, RetrieveFoldersUseRestful and change the value from false to true
5. Save the file
6. Restart the Docu Performer
7. Try again the sync or documentation

Solution 3 (hide favorites folder)

In some cases loading the folder structure fails, then we need a "false".

...