row_number in 5.7.18-log

[Consultant Fifi]

Hi, This is my stored procedure which was working fine in 5.6 but after we upgrated to 5.7.18-log it isn't performing as before.
What happens is we add items in a list (tablelist ). If we add it (item_id) between line 3 and 4 (pos)then it's postion becomes 4 and all the rest below in the list, their position get bumped forward accordingly. It was working fine but now even if we select any place in the list, it gets added to the end of list.
UPDATE tablelist AS A
INNER JOIN (
SELECT l.id,
l.pos,
@curRow := @curRow + 1 AS row_number
FROM tablelist l
JOIN (SELECT @curRow := 0) r
WHERE l.item_id = iItemID
ORDER BY l.pos, l.id DESC ) AS B
ON A.id = B.id
SET A.pos = lpad(B.row_number, 4, '0')
WHERE A.item_id = iItemID;
SET @NewLineNo = (
SELECT pos
FROM tablelist
WHERE item_id = iItemID
);

Please can you help me to get this sorted.