VMware backups failing with status code 6/23

Hi, 

Please help me to solve this problem.

My enviroment:

Masterserver: NBU 7.6.0.4

VMware: ESX 5.5

Logs from job details:

2/23/2015 6:02:15 PM - Info nbjm(pid=3052) starting backup job (jobid=1084) for client HCM-MAIL-MB1, policy mail1.vmware.san, schedule Full  
2/23/2015 6:02:15 PM - estimated 0 Kbytes needed
2/23/2015 6:02:15 PM - Info nbjm(pid=3052) started backup (backupid=HCM-MAIL-MB1_1424689335) job for client HCM-MAIL-MB1, policy mail1.vmware.san, schedule Full on storage unit mediaserver-hcart3-robot-tld-0
2/23/2015 6:02:15 PM - started process bpbrm (22706)
2/23/2015 6:02:17 PM - connecting
2/23/2015 6:02:17 PM - connected; connect time: 0:00:00
2/23/2015 6:02:18 PM - mounting PEP013
2/23/2015 6:02:25 PM - end writing
2/24/2015 1:01:43 AM - Info bpbrm(pid=22706) HCM-MAIL-MB1 is the host to backup data from     
2/24/2015 1:01:43 AM - Info bpbrm(pid=22706) reading file list for client        
2/24/2015 1:01:43 AM - Info bpbrm(pid=22706) starting bpbkar on client         
2/24/2015 1:01:44 AM - Info bpbkar(pid=7976) Backup started           
2/24/2015 1:01:44 AM - Info bpbrm(pid=22706) bptm pid: 22710          
2/24/2015 1:01:44 AM - Info bpbkar(pid=7976) archive bit processing:<enabled>          
2/24/2015 1:01:44 AM - Info bptm(pid=22710) start            
2/24/2015 1:01:44 AM - Info bptm(pid=22710) using 65536 data buffer size        
2/24/2015 1:01:44 AM - Info bptm(pid=22710) using 30 data buffers         
2/24/2015 1:01:44 AM - Info bptm(pid=22710) start backup           
2/24/2015 1:01:44 AM - Info bptm(pid=22710) backup child process is pid 22713       
2/24/2015 1:01:44 AM - Info bptm(pid=22710) Waiting for mount of media id PEP013 (copy 1) on server mediaserver. 
2/24/2015 1:01:49 AM - Error bpbrm(pid=22706) from client HCM-MAIL-MB1: ERR - Error opening the snapshot disks using given transport mode: Status 23
2/24/2015 1:01:50 AM - Error bptm(pid=22710) media manager terminated during mount of media id PEP013, possible media mount timeout
2/24/2015 1:01:50 AM - Error bptm(pid=22713) system call failed - Connection reset by peer (at child.c.1306)   
2/24/2015 1:01:50 AM - Error bptm(pid=22713) unable to perform read from client socket, connection may have been broken 
2/24/2015 1:01:51 AM - Error bptm(pid=22710) media manager terminated by parent process       
2/24/2015 1:01:51 AM - Error bpbrm(pid=22706) could not send server status message       
2/24/2015 1:01:51 AM - Critical bpbrm(pid=22706) unexpected termination of client HCM-MAIL-MB1        
2/24/2015 1:01:51 AM - Info bpbkar(pid=0) done. status: 6: the backup failed to back up the requested files 
the backup failed to back up the requested files(6)

Log from VxMS_provider:

See attachment.

Thank you.

Tuan.