Can't Delete from 'Videos'

Running Win 10 on an SP4.

I have a bunch of .mp4 files in my "users\Videos" subdirectory. I cut-and-pasted them to a new location.

They are in the new location.

They still appear - but with a "generic" (i.e., not "thumbnail") icon. They are not playable ("We can't get to this file... 0xc101aa"), and I can not delete them.

When I try in Explorer, they disappear. Then reappear. When I try in Command Prompt (Admin), I get "Access is denied".

I don't have any automatic syncing set up (and this is nowhere near my OneDrive directories).

I believe the word I'm looking for is "Aargggh!"

Have you installed any folder protection software?
For example, if your video files are protected with a software like "Protect My Folders", they will be hidden from Windows Explorer and you're also unable to access them from Command Prompt.