Mmmz I am wondering.....
On the VSA performing the job for that subclient:
Stop Commvault services, move the following folder to for instance c:\temp and start services again:
Here are possible file locks within the VDDK proces, folder will be created again when a new job is running.
p.s. if you want to delete the folder you will have to take ownership, add full access rights for your account, remove read only attribute and delete the folder..
Moving the folder does not require these actions.