Within the ServiceSettings.xml of the Windows client you are able to disable the following of symbolic links, junction and reparse points.
The ServiceSettings.xml can be found in the following directory:
C:\ProgramData\OnlineBackupClient
First you have to close the client and stop the OnlineBackupService.
Open the ServiceSettings.xml in notepad or a similar application.
Edit the following line:
<DoJunctionsBackup>True</DoJunctionsBackup>
By default this is set to 'True', so change this to 'False'.