The solution
When override is enabled, you can prevent configuration changes from being lost by doing the following:
• Verify that all cluster units are operating before making configuration changes (from the web-based manager go to System > Config > HA to view the cluster members list or from the FortiOS CLI enter get system ha status).
• Make sure the device priority of the primary unit is set higher than the device priorities of all other cluster units before making configuration changes.
• Disable override either permanently or until all configuration changes have been made and synchronized to all cluster units.