Technical Tip: 'An error occurred when attempting to change this reference (system.interface), this reference must be handled manually when trying to migrate Vlans.

The following picture illustrates the point clearly. The error occurs when migrating the VLANs from one port to another on FortiGate using the 'Migrate' feature.

1. If FortiGate has identified a situation where migration using the tool is not feasible, it is clear that the only way to implement the necessary changes is through manual processes.
   
   
2. Note that when using FortiConverter, the results will remain unchanged, as the VLAN configuration does not get migrated. VLAN configuration will need to be added manually.
   

Related article:

Troubleshooting Tip: 'An error occurred when attempting to change this reference (system.zone), this reference must be handled manually.' when trying to add interface to SD-WAN zone with Integrate Interface option on GUI