Folder List on remote server not fully displayed.

I have a small network of machines running Win10. All are activated, some were upgrades and then ISO installed to check. Some were Technical Preview installations. Some are FAST ring and some are SLOW ring.
They all connect to a NAS to share files in folders and keep backups.
Recently I had a report that not all the NAS folders were being displayed. When I checked from the master machine (Win 7) all the folder were displayed some 22 in all. So I checked the individual Win 10 machines. All the Win 10 machines that had not been updated to 10525 showed the same number of folders, 3 less than the master machine and the Win 10 FAST ring number.

Now I am puzzled why there should have been such a difference.
The folders not being displayed where the root folder (C), Admin, and Home.
I checked the folder view options and Show all hidden files was selected.

NAS = Netgear ReadyNAS NV+

Can anyone suggest a reason why the latest build shows all the folders and the earlier ones do not?

are the Windows 10 clients using Administrator accounts or just User accounts?

For the moment they are all administrator accounts.

A further update to the puzzle.
One of my machines is a laptop which I had split into two machines Win7 and Win10. The Win10 was initially a technical preview but has been upgraded to be an ISO installed version. It was configured to be on the Fast ring and has just received the latest evaluation copy (build 10525). This is showing the same difference in the number of folders on the NAS. Prior to the recent update it was showing the lower number 19 instead of 22 (the real number). Now it is showing all the folders on the NAS 22.
Anyone got any ideas as to why the difference?
The three missing folders are apparently associated with the software installed in the NAS. Almost as if the O/S in the NAS has allowed access to hidden or system folders.