[mdlug] Copying files from one mounted drive to another mounted drive on Pi

[email5000 at usa.com]

I think I'm missing something...

I have two mounted drives on my Pi - my NAS and another HDD in a USB
case that I'm using to backup the data. I've copied data to/from the NAS
before; and regarding TO the NAS to the Pi, I needed to change the
permissions on the mount point to allow the writing. I've done all that.

I presently have two 'file explorer' type windows - obviously one for
the NAS and one for the external HDD.  Obviously both are mounted. As
far as I can tell, all permissions are copacetic. When I attempt to
'drag-and-drop'  the folder on the NAS to the folder on the USB HDD, the
file image being dragges scoots back to the other side.

What am i missing?

Thanks.