diff --git a/db/routines/vn/procedures/collection_assign.sql b/db/routines/vn/procedures/collection_assign.sql
index ba83f1fbb..a4c861c96 100644
--- a/db/routines/vn/procedures/collection_assign.sql
+++ b/db/routines/vn/procedures/collection_assign.sql
@@ -3,7 +3,7 @@ CREATE OR REPLACE DEFINER=`vn`@`localhost` PROCEDURE `vn`.`collection_assign`(
 	vUserFk INT,
 	OUT vCollectionFk INT
 )
-BEGIN   
+BEGIN
 /**
  * Comprueba si existen colecciones libres que se ajustan
  * al perfil del usuario y le asigna la más antigua.
@@ -45,6 +45,12 @@ BEGIN
 	DECLARE CONTINUE HANDLER FOR NOT FOUND SET vDone = TRUE;
 	-- Si hay colecciones sin terminar, sale del proceso
 
+	DECLARE EXIT HANDLER FOR SQLEXCEPTION
+	BEGIN
+		ROLLBACK;
+		RESIGNAL;
+	END;
+
 	CALL collection_get(vUserFk);
 
 	SELECT (pc.maxNotReadyCollections - COUNT(*)) <= 0, pc.maxNotAssignedCollectionLifeTime 
@@ -118,9 +124,19 @@ BEGIN
 	IF vCollectionFk IS NULL THEN
 		CALL collection_new(vUserFk, vCollectionFk);
 
-		UPDATE `collection`
-			SET workerFk = vUserFk
-			WHERE id = vCollectionFk;
+		START TRANSACTION;
+
+		SELECT workerFk INTO vCollectionWorker
+			FROM `collection` 
+			WHERE id = vCollectionFk FOR UPDATE;
+
+		IF vCollectionWorker IS NULL THEN
+			UPDATE `collection`
+				SET workerFk = vUserFk
+				WHERE id = vCollectionFk;
+		END IF;
+
+		COMMIT;
 	END IF;
 END$$
 DELIMITER ;
\ No newline at end of file
diff --git a/db/routines/vn/procedures/sale_getProblems.sql b/db/routines/vn/procedures/sale_getProblems.sql
index 2bba8fbc3..b50b4784d 100644
--- a/db/routines/vn/procedures/sale_getProblems.sql
+++ b/db/routines/vn/procedures/sale_getProblems.sql
@@ -40,7 +40,7 @@ BEGIN
 		isTooLittle BOOL DEFAULT FALSE,
 		isVip BOOL DEFAULT FALSE,
 		PRIMARY KEY (ticketFk, saleFk)
-	) ENGINE = MEMORY;
+	); -- No memory
 
 	INSERT INTO tmp.sale_problems(ticketFk,
 									saleFk,