This was a known issue at software versions below 3.1.2. If you have not already done so upgrade your vmPro to 3.1.2. This should prevent the issue from occurring again however you will need to manually clean up any folders that are outside of the retention policy.
To do this, mount the UNC path to the storage share utilized by vmPro, then delete any folders created by vmPro that are outside the retention policy time frame.