i believe you are are using the SLP to perform this duplications..

could you show us the SLP configurations... may be a Screenshot of it 

or the command 

nbstl <SLP name> -L 

and the detail status of the duplication job

I agree with Nagalla - we need to see how duplication/SLP is configured and how it is interpreted by NBU in job details.

It sounds like incorrect STU is selected.

NetBackup 7.5 Best Practice - Using Storage Lifecycle Policies

Storage Lifecycle Policy (SLP) Cheat Sheet

 Storage Lifecycle Policy Tricks and Tips

https://www-secure.symantec.com/connect/blogs/storage-lifecycle-policy-tricks-and-tips

here is an activity monitor log :

awaiting resource 000047 A pending request has been generated for this resource request.
     Operator action may be required. Pending Action: No action.,
     Media ID: 000047, Barcode: 000047, Density: hcart3, Access Mode: Read,
     Action Drive Name: N/A, Action Media Server: sp-svg-002lds, Robot Number: N/A, Robot Type: NONE,
     Volume Group: 000_00001_TLD, Action Acs: N/A, Action Lsm: N/A

hello,

N.B :

SITE A = Auber (Disk Storage is : ST_DISK_AUBER; For Tape :storage is :  the volume Group TAPE-AUBER) --> The media server control host is : sp-svg-002lds

SITE B = CROIS (Disk Storage is : ST_DISK_CROIS; For Tape :storage is :  the volume Group TAPE-CROIS) --> The media server control host is : sp-svg-003lds

so, here is the result of the commaand nbstl :

[root@sp-svg-002lds ~]# nbstl  M_AU-CR-TAPE_CR -L
                                Name: M_AU-CR-TAPE_CR
                 Data Classification: (none specified)
            Duplication Job Priority: 0
                               State: active
                             Version: 9
 Operation  1                Use for: 0 (backup)
                             Storage: ST_DISK_AUBER
                         Volume Pool: (none specified)
                        Server Group: (none specified)
                      Retention Type: 0 (Fixed)
                     Retention Level: 8 (1 year)
               Alternate Read Server: (none specified)
               Preserve Multiplexing: false
      Enable Automatic Remote Import: false
                               State: active
                              Source: 0 (client)
                        Operation ID: (none specified)
                     Operation Index: 1
                         Window Name: --
                 Window Close Option: --
                Deferred Duplication: no
 Operation  2                Use for: 1 (duplication)
                             Storage: TAPE-AUBER
                         Volume Pool: Mensuelle
                        Server Group: Any
                      Retention Type: 0 (Fixed)
                     Retention Level: 8 (1 year)
               Alternate Read Server: sp-svg-002lds
               Preserve Multiplexing: true
      Enable Automatic Remote Import: false
                               State: active
                              Source: Operation 1 (backup:ST_DISK_AUBER)
                        Operation ID: (none specified)
                     Operation Index: 2
                         Window Name: Default_24x7_Window
                 Window Close Option: SFN
                Deferred Duplication: no
 Operation  3                Use for: 1 (duplication)
                             Storage: ST_DISK_CROIS
                         Volume Pool: (none specified)
                        Server Group: (none specified)
                      Retention Type: 0 (Fixed)
                     Retention Level: 8 (1 year)
               Alternate Read Server: sp-svg-003lds
               Preserve Multiplexing: false
      Enable Automatic Remote Import: false
                               State: active
                              Source: Operation 1 (backup:ST_DISK_AUBER)
                        Operation ID: (none specified)
                     Operation Index: 3
                         Window Name: Default_24x7_Window
                 Window Close Option: SFN
                Deferred Duplication: no
 Operation  4                Use for: 1 (duplication)
                             Storage: TAPE-CROIS
                         Volume Pool: Mensuelle
                        Server Group: Any
                      Retention Type: 0 (Fixed)
                     Retention Level: 8 (1 year)
               Alternate Read Server: sp-svg-003lds
               Preserve Multiplexing: true
      Enable Automatic Remote Import: false
                               State: active
                              Source: Operation 3 (duplication:ST_DISK_CROIS)
                        Operation ID: (none specified)
                     Operation Index: 4
                         Window Name: Default_24x7_Window
                 Window Close Option: SFN
                Deferred Duplication: no

Here is an activity Monitor log :

awaiting resource 000047 A pending request has been generated for this resource request.
     Operator action may be required. Pending Action: No action.,
     Media ID: 000047, Barcode: 000047, Density: hcart3, Access Mode: Read,
     Action Drive Name: N/A, Action Media Server: sp-svg-002lds, Robot Number: N/A, Robot Type: NONE,
     Volume Group: 000_00001_TLD, Action Acs: N/A, Action Lsm: N/A

Alternate Read Server: sp-svg-002lds

You have specified an Alternate Read Server in Operation 1 of the SLP. 
Does media server sp-svg-002lds  have access to the backup source?  
 

Same for 
 Operation  3                Use for: 1 (duplication)
                                     Alternate Read Server: sp-svg-003lds
                                            Source: Operation 1 (backup:ST_DISK_AUBER)

and
Operation  4                
               Alternate Read Server: sp-svg-003lds
                                            Source: Operation 3 (duplication:ST_DISK_CROIS)
 

You also forgot to show us information in Details tab of the duplication job.

We also need to see Storage Unit Group config:

bpstulist -L -g

yes.. next step is to see the Storage units in the Storage unit groups

hello,

for the operation1, we cannot pecify an Alternate Read Server, cause it's a backup operation.

so, the detail tab of the duplication is :

awaiting resource 000047 A pending request has been generated for this resource request.
     Operator action may be required. Pending Action: No action.,
     Media ID: 000047, Barcode: 000047, Density: hcart3, Access Mode: Read,
     Action Drive Name: N/A, Action Media Server: sp-svg-002lds, Robot Number: N/A, Robot Type: NONE,
     Volume Group: 000_00001_TLD, Action Acs: N/A, Action Lsm: N/A

The Result of bpstulist -L -g :

[root@sp-svg-002lds ~]# bpstulist -L -g

Label:                ST_TAPE_AUBER_SP-SVG-002LDS
Storage Unit Type:    Media Manager
Host Connection:      sp-svg-002lds
Number of Drives:     2
On Demand Only:       no
Density:              hcart3 (20)
Robot Type/Number:    TLD (8) / 0
Max Fragment Size:    1048575
Max MPX/drive:        18

Label:                ST_TAPE_AUBER-DXI6702
Storage Unit Type:    NDMP
Host Connection:      sp-svg-002lds
Number of Drives:     2
On Demand Only:       no
Density:              hcart3 (20)
Robot Type/Number:    TLD (8) / 0
Max Fragment Size:    20480
Max MPX/drive:        1
NDMP attach host:     LDS-AUBER-DXI6702-01

Label:                ST_TAPE_CROIS_SP-SVG-003LDS
Storage Unit Type:    Media Manager
Host Connection:      sp-svg-003lds
Number of Drives:     2
On Demand Only:       no
Density:              hcart3 (20)
Robot Type/Number:    TLD (8) / 1
Max Fragment Size:    1048575
Max MPX/drive:        18

Label:                ST_TAPE_CROIS-DXI6702
Storage Unit Type:    NDMP
Host Connection:      sp-svg-003lds
Number of Drives:     2
On Demand Only:       no
Density:              hcart3 (20)
Robot Type/Number:    TLD (8) / 1
Max Fragment Size:    20480
Max MPX/drive:        1
NDMP attach host:     LDS-CROIS-DXI6702-02

Label:                ST_DISK_AUBER
Storage Unit Type:    Disk
Media Subtype:        DiskPool (6)
Host Connection:      sp-svg-002lds
Concurrent Jobs:      40
On Demand Only:       yes
Robot Type:           (not robotic)
Max Fragment Size:    524288
Max MPX:              1
Block Sharing:        no
File System Export:   no
Ok On Root:           no
Disk Pool:            LSU-AUBER
Snapshots:            no
Replication Primary:  no
Replication Source:   no
Replication Target:   no
Mirror            :   no
Independent       :   no

Label:                ST_DISK_CROIS
Storage Unit Type:    Disk
Media Subtype:        DiskPool (6)
Host Connection:      sp-svg-003lds
Concurrent Jobs:      40
On Demand Only:       yes
Robot Type:           (not robotic)
Max Fragment Size:    524288
Max MPX:              1
Block Sharing:        no
File System Export:   no
Ok On Root:           no
Disk Pool:            LSU-CROIS
Snapshots:            no
Replication Primary:  no
Replication Source:   no
Replication Target:   no
Mirror            :   no
Independent       :   no
__GROUPS__
TAPE-AUBER 1 ST_TAPE_AUBER_SP-SVG-002LDS
TAPE-CROIS 1 ST_TAPE_CROIS_SP-SVG-003LDS
[root@sp-svg-002lds ~]#

STU groups looks fine.. since they have only once STU on each..

SLP version is 9, means the SLP is modified 9 times since its created...

may be the images that you are having the issue associated with old versions that are having the wrong configurations..

could you post the output of below command to list all versions

nbstl <SLP name> -L -all_versions

once we see the versions output .... if the issue is with the verison, we can modifify the versions to the correct one..