Hi yeow_km,
This has to do with your backups. When EV archives data, it stores it in the aforementioned vault store partitions. Normally EV will wait for these to be backed up before converting the archived content into shortcuts. One way to do this is by the archive bit. Typical backups look like this:
1. EV archiving run
2. Vault store partition placed in backup mode
3. Partitions are backed up and files in the partitions have their archive bits reset
4. Backup mode is set to off, EV checks vsps and finds then to be backed up
5. Shortcut processing.
I would suggest you check to ensure your backup solution is backing up EV in a timely manner and that it is sticking the VSPs in backup mode.