Why My Book 3TB folders are partially visible?

I have this strange problems happens very often that I have some folders, and some of them are fully visible, all files in the folders can show up, but other folders then show up as “empty” -  the exact message in WIndows File Browser is " This Folder is Empty". However, the folder is NOT empty, and some other times, I might be able to see the content again.

Does anybody know why and how I can be able to see all content?

Thanks!

Did you check if the same problem happens on any PC? 

Try deleting the driver for the drive, disconnect it,reboot PC, then reconnect the drive. That will load a fresh driver.

Joe