My Book - Win10 .. files disappear & then reappear!

Hi

I have just purchased a 3tb Mybook external HD & connected to my win10 PC

I have transferred around 500gb of my music files to drive - however every folder i open, all files immediately disappear, then one by one they re-appear. It’s very annoying especially if there are loads of files in folder

Any ideas

The firmware on the My Book has not been updated for a long time

better is to have a desktop with an extra hard disk for media, the WD disks are fine for media libraries galore