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.