DigitalVolcano Software Support

The popular archiving software, 7-zip, has an option to split the archive into multiple volumes. If you do this, it generates a set of files with volume names such as output.zip.001, output.zip.002, etc.. It appears to me that if you use 'same file name' and 'ignore content' in Duplicate Cleaner, all of these files are classified as duplicates even though the file names are different.

Have you tried turning the 'Ignore file extensions when comparing names' option off? It's in the More Options window->Scanning tab.

That was the problem. I don't remember why or when I turned that on, but clearly I must have.
Thanks.