NetBackup SSO - issues writing to tape library across the domain

I am having some issues in writing to a shared (SSO) library from across the AD domain. We have capacity based licensing model using NetBackup version 7.1.0.4

There are 2 x AD domains A.local & B.com: There is a firewall between the two AD domains. However, upon request all the ports for AD and NBU across the firewall have been allowed. The name resolution has been tested.

The A.local domain has 1 x NBU Master and 2 x Media servers (on seperate physical boxes) running on Windows 2008 R2.  The shared tape library (4 drives) is zoned to one of the Media server in A.local domain. The 4 drives are also shared for NDMP backups.

Issue:

Now, a new Media server on Windows 2008 R2 in B.com domain has been introduced connected to the NetBackup Master server in A.local. The new Media server is able to communicate with the Master server and completing successful backups (of some B.com domain clients, some failing with handshaking issues) to the storage disk pool attached to this Media server. I managed to add the library and all 4 x drives through the storage configuration wizard and it allows me to create storage pool.

When I try to duplicate the backups from B.com Media server using the tape library connected to A.local Media server, the duplicate job hungs with error "the drives are down". When I look at the device status, the drive showing the new media server name against it shows AVR mode.

On the new media server i ran "vmoprcmd -d -h", the output is as follows;

PENDING REQUESTS

                                     <NONE>

                                  DRIVE STATUS

Drv Type   Control  User      Label  RecMID  ExtMID  Ready   Wr.Enbl.  ReqId
  0 hcart2   AVR                -                     No       -         0
  1 hcart2   AVR                -                     No       -         0
  2 hcart2   AVR                -                     No       -         0
  3 hcart2   AVR                -                     No       -         0

                             ADDITIONAL DRIVE STATUS

Drv DriveName            Shared    Assigned        Comment
  0 SL500-P2_LTO5_D1      Yes      -
  1 SL500-P2_LTO5_D2      Yes      -
  2 SL500-P2_LTO5_D4      Yes      -
  3 SL500-P2_LTO5_D3      Yes      -