R7000P Readyshare phantom files with windows Robocopy

Running Win10 2H22 pro 64 bit, using Robocopy to pull archive from network share drive (hosted on Netgear R7000P "readyshare" running V1.3.2.134_10.1.66  firmware) to local HDD.

Windows command was:  robocopy \\share\Memory_Alpha    \ "G:\Memory Alpha"   /DST /E /FFT /PURGE

Everything did what it should, EXCEPT for three directories two levels down from the "root"

- A set of files that had been deleted many weeks ago were shown to be on the network drive, and were shown to have been copied over by Robocopy
- Except...nothing was in either the source or the destination drive by those filenames
- Did several brute-force searches to try to find them - nothing
- Did disk check and there were no errors on either the source or the destination drive
- Did a search for System or Hidden attributes -- none in the file tree

- Ran Robocopy again and it just reported that the two directory trees were fully in sync

My only theory is that the Netgear file system had cached the deleted file names and hadn't updated its cache upon their deletion....and then Robocopy reported their being copied over, even though there was nothing to copy. I would have expected Robocopy to report some sort of error, but it did not.  The odd thing is that both the Netgear and the client PC had been rebooted since those files had been deleted, so this theory doesn't hold up so well.

Anybody else seeing this?