src/classes/Models/Server.php

@@ -33,7 +33,9 @@ class Server extends \Friendica\Directory\Model
 			SET `server_id` = :server_id,
 				`alias` = :alias,
 				`timestamp` = NOW()
-			ON DUPLICATE KEY UPDATE `timestamp` = NOW()',
+			ON DUPLICATE KEY UPDATE 
+				`server_id` = :server_id,
+				`timestamp` = NOW()',
 			[
 				'server_id' => $server_id,
 				'alias' => strtolower($server_alias)

src/sql/migrations/up/0007.sql

@@ -0,0 +1,6 @@
+BEGIN;
+CREATE TABLE temp_server_alias AS SELECT * FROM server_alias GROUP BY alias;
+DROP TABLE server_alias;
+RENAME TABLE temp_server_alias TO server_alias;
+CREATE UNIQUE INDEX server_alias_alias_uindex ON server_alias (alias);
+COMMIT;