The DLO Policy applied to the user will have Revision Control settings that control how long to keep items for - this might help you get rid of them.
There is also a deleted item retention option.
Both these items are in the Properties of Each of the Backup Selections i.e. if you click My Music in the Profile and Click Modify you will find them. - As such not sure how you trigger them when you have unchecked the selection that controlled them
You might be able to set to keep 0 revision in the Network User Data Folder and then set Delete user Data after 1 day (against the My Music Selection) then re-enable then wait a couple of days then re-disable it.
Bear in mind that even though the files you are trying to remove are held on the server the housekeeping task itself is requested by the DLO Client - so files will only be removed that meet the deletion rules - when a user is logged in.