FMG v6.x - Registering Fortigate in Backup mode always reverts to Normal mode

[Francis]

Hi everyone,

We want to use our FortiManager only in backup mode. However, any registered fortigate always reverts to Fully Managed (normal) mode after a while. Is this a known bug or am I making a wrong config somewhere ?

relevant config:

config system central-management
    set type fortimanager
    set mode backup
    set schedule-config-restore disable
    set schedule-script-restore disable
    set allow-push-configuration disable
    set fmg "x.x.x.x"
    set fmg-source-ip x.x.x.x
    config server-list
        edit 1
            set server-type update rating
            set server-address x.x.x.x
        next
    end
end

After a while the 'set mode backup' line disappears from the config and we are again forced to select 'read-only' or 'read-write' at login time.

[chall_FTNT]

Is this FortiGate assigned to a FortiManager ADOM that is in backup mode?