I have a problem with MySQL creating a counter variable SOrder based on a set order defined by order by. It was working in MySQL 5.1 but currently not in 5.7. Original query in 5.1 had the subquery order by and was acceptable to the standards back then. Under 5.7 with only_full_group_by mode off, I added the order by to the outside but even when the order by within the subquery was commented out (or ignored according to SQL standards), it output SOrder as if it's random but not based on Column Carrier, PRIOR, ShipMethod, SingleModel.

SELECT 
    Carrier,
    PRIOR,
    ShipMethod,
    GroupOrder,
    @row_no:=IF(@prev_val = ANY_VALUE(t.SingleModel),
        @row_no,
        @row_no + 1) AS 'SOrder',
    SingleModel,
    COUNT(t.SingleModel) AS 'SingleModelTotQty',
    @prev_val:=ANY_VALUE(t.SingleModel)
FROM
    (SELECT 
        CASE
            WHEN ANY_VALUE(W.hdr_user_defined_field18) LIKE '%Fedex%' THEN 'FEDEX'
            ELSE 'UPS'
        END AS 'Carrier',
        CASE
            WHEN
                ANY_VALUE(W.hdr_user_defined_field20) IN ('16' , '26', '45', '88', '96')
                        OR ANY_VALUE(W.hdr_user_defined_field20) IN ('19' , '21', '22', '23', '24', '44', '76', '77', '78')
            THEN 'PRIOR'
            ELSE 'NORM'
        END AS 'PRIOR',
        CASE
            WHEN
                ANY_VALUE(W.hdr_user_defined_field20) IN ('88' , '96', '80', '97')
                    OR ANY_VALUE(W.hdr_user_defined_field20) IN ('76' , '77', '78', '79')
                    OR ANY_VALUE(W.`Ship-To Location`) != ''
            THEN 'S2S'
            ELSE 'S2H'
        END AS 'ShipMethod',
        CASE
            WHEN SUM(Quantity) = 1 THEN 'Single'
            WHEN
                SUM(Quantity) > 1 AND COUNT(`PO Number`) = 1
            THEN 'Multiple'
            WHEN COUNT(`PO Number`) > 1 THEN 'Mixed'
        END AS 'GroupOrder',
        CASE
            WHEN SUM(Quantity) = 1 THEN `Supplier Item Nbr`
            WHEN SUM(Quantity) > 1
                    AND COUNT(`PO Number`) = 1
            THEN ' '
            WHEN COUNT(`PO Number`) > 1 THEN ' '
        END AS 'SingleModel',
        `PO Number` AS 'PONUM',
        CASE
            WHEN SUM(Quantity) = 1 THEN ' '
            ELSE SUM(Quantity)
        END AS 'QtyPerMulPO'
    FROM
        dropship.Walmart_FullPOs W
    WHERE
        ProcessedDate = CURDATE() - 5
    GROUP BY `PO Number`
    **ORDER BY Carrier , PRIOR DESC , ShipMethod , GroupOrder DESC , SingleModel DESC**
    ) t,
    (SELECT @row_no:=0) x,
    (SELECT @prev_val:='') y
WHERE
    GroupOrder = 'Single'
GROUP BY Carrier , PRIOR , ShipMethod , SingleModel
ORDER BY t.Carrier , t.PRIOR DESC , t.ShipMethod , t.GroupOrder DESC , t.SingleModel DESC

Result