Did you have made some change on Permission for deletion with the last update (2016.3.1018)?
After update, Permission for Deletion not works like before update.
I set permission with a customprovider (permission is ok on GetPermissions return after update too))
Windows Security are ok too.
The button changes to enable just if Parent Folder have access on Deletion and not take care about the permission of file.
Thank you for your help.