Operating System locks up post rsync to External USB drive.

I have tried the external drive on every USB slot.  The issue is further exacerbated by having to perform a dirty shutdown, which corrupts permissions on the NAS.  Syncing the permissions with AD does no good.

To clarify, when trying to perform a backup to an external drive, regardless of the USB port, the NAS O/S seems to hang after a few hours.  I cannot access the admin page, but I can SSH into the system.  Also, I can access the shares without any problem.  The backup never completes.  When issuing the restart or poweroff commands from within an SSH terminal session, the session seems to hang and never returns to the command prompt.  The only way to return the NAS to operation is to force a shutdonw by pressing the power buttin for about 10 seconds.  As you may know, this causes problems and I have to reenter all permissiond on all shares.

Additionally, one user is unable to access their home share.  I can access the files through the admin panel (after rebooting the NAS), but the specific user receives an "access denied.  You do not have permission to access this folder" error.

I have tried the orderly shotdown procedure using the power button, but the NAS does not respond.  The access/activity light on the external USB connected drive flashes once every 2.5 seconds, continuously.

Do you need anything from me to resolve the issue?