Confirm the images are local, accessible, and inside the selected folder. Check Settings → Scanning → Similar Photos and lower the minimum only when needed.
Similarity is an algorithmic comparison, not an identity test. Crops, rotations, edits, exposure, format, orientation, aspect ratio, and resolution can change grouping. Try Almost Identical, Similar, and Broad Match before deciding that an image is missing or grouped incorrectly.
After editing or replacing photos, start a new scan rather than relying on results that are already open. diCleaner checks changed photos again during the new scan.
Use Duplicate Files Finder for exact-content copies. Review every visual group manually before removing anything.
For a likely incorrect result, preserve the images and report their formats, dimensions, sizes, and redacted examples when you are comfortable sharing them.