It means that you have 2 tag fields of the type YEAR - see the extended tags dialogue which should show YEAR twice.
You can remove such fields with an action of the type "Remove duplicate fields".
Multi-value fields are according to standard.
It means that you have 2 tag fields of the type YEAR - see the extended tags dialogue which should show YEAR twice.
You can remove such fields with an action of the type "Remove duplicate fields".
Multi-value fields are according to standard.