External volumes can maintain Trash data separately from the startup disk.
Connect and unlock the volume, confirm it appears in Finder, and keep it mounted through scanning and removal.
Review every item and restore anything needed before emptying. A file in external Trash may be the only copy.
Permissions and ownership can depend on the user who trashed the item. Full Disk Access does not make a read-only disk writable.
If the disk disconnects, stop and reconnect it before running a new scan. Do not reuse the stale result.
The Trash tool can vary by diCleaner edition.