The bug has been marked "Not Fixed" in Fuse 6.2.1
As a workaround you can try this:
Certain properties of the resource Exchange need to be copied over to the original Exchange for the Camel markerFile to be deleted correctly.
These properties are dynamic in their names but append Exchange.FILE_LOCK_FILE_ACQUIRED and Exchange.FILE_LOCK_FILE_NAME at the end of their names.
An alternative is to copy all properties of the resource Exchange to the original Exchange but this *may* overwrite existing Exchange properties.