We're having an odd issue where our Zimbra backups disappear out of the administrative web control panel. The server is configured to run the "Standard" backup schedule, according to the Configuration > Global Settings > Backup/Restore tab (i.e. run a full backup once a week, and run incremental backups daily during the week). Here's what we're seeing:

Yesterday (12/12), we had four backup files visible in the admin web console:

- Full backup from 12/9
- Full backup from 12/10
- Incremental backup from 12/11
- Incremental backup from 12/12

The same files (and no other files) were visible when we SSHed into the server.

Today (12/13), we had one backup file visible in the admin web console:

- Incremental backup from 12/13

However, all of the files from the previous day (both full backups, and all three incremental backups) were visible when we SSHed into the server.

Any ideas what's going on? We recently switched to using a NAS drive to store all the backups (about 2 weeks ago), mounted at "/opt/zimbra/backup/", so this may be at fault, but we haven't had any problems with the NAS drive before, so I'm not sure why it would suddenly start causing problems.