NDMP restore occurs on Non NDMP drive

[Fredje]

Hi,

I got a problem with the restore of an NDMP backup.

NetBackup 6.0 MP4
1 RedHat Master Server
1 NAS bay
1 Scalaar i500 (with 3 drives)

1st drive (piloting the robotic) is directly connected on the master (Standard Media Manager)
The 2 others are directly connected to the NAS Bay as NDMP

Backups are running good up to now (NDMP policy on NDMP STU)
When I try to restore an NDMP backup of the NAS (via GUI as described in the NDMP Guide) the Master/Media server want to mount the volume on the "Media Manager Tape Drive" (STU of the server) causing the restore to fails.
As I manually set the MediaManager drive to down state the restore occurs on the NDMP drive and is successful.

How can I force the restore to occur on the NDMP STU without setting the MM drive down?
Need I to create an NDMP STU for the Master Server?

Did anyone already meet this problem?

Thanks a lot in advance!!