PR4100 - cannot delete folders in a share

Hello - I have a share setup on a PR4100, called vBackup. Within that share are various folders corresponding to dated backups. I need to delete some older ones. I changed permissions on the NAS , admin user, to read/write…it worked for awhile and then I was blocked from deleting folders. Rebooted, latest firmware, etc. What am I missing?

Thank you