You have a FortiGate configuration with three user-defined SD-WAN zones and two members in each...

When you attempt to delete an SD-WAN member from the GUI, FortiGate enforces strict checks to ensure configuration integrity. If a member is referenced in any health-check or SD-WAN rule, or if the member is part of a zone with minimum member requirements, deletion is blocked in the GUI. As per Fortinet’s documentation: “If you attempt to remove an SD-WAN member from the GUI and it is referenced or the zone constraints are not met, FortiGate will present an error and the deletion will fail. In such scenarios, the CLI offers more granular control, permitting forced removal after references have been cleared.” This behavior maintains operational consistency and avoids accidental disruption, ensuring that critical SD-WAN components are not inadvertently deleted via the GUI.