Hi All,
I've encounter this issue multiple times, figured it out multiple times and then forgotten my solution ... multiple times. The issue for me turned out to be that the folder/files could not be deleted because they had the "compress ..." attributes enabled. Check the folder/file by right-clicking it > Properties > Advanced (general tab) > uncheck "Compress contents to save disk space". After this, I was able to use the Duplicate File Finder deletion without issue.
Hopefully this helps someone, especially Piriform, to understand the issue.
Good luck!
- Jeremy
