SQL0802N might happen for SUM() function in specific SQL statements with DB2 V11.1

Symptom

A SQL statement failed with SQL0802N Arithmetic overflow or other arithmetic exception occurred .
And the generated optimized statement was like the following example. It was different from the optimized statement with V10.5.

Example:

Original Statement:
------------------
SELECT ...

(SELECT SUM(T1.C1) FROM T1 WHERE T1.C2 = T2.C1)
...
(SELECT SUM(T1.C1) FROM T1 WHERE T1.C2 = T2.C1)
...
(SELECT SUM(T1.C1) FROM T1 WHERE T1.C2 = T2.C1)
...
) FROM T2

Nore:
The original statement has multiple subselect. They were rewritten to the following subselect using "group by".

Optimized Statement:
-------------------
SELECT ...

     (SELECT
        Q11.$C0
      FROM
        (SELECT
           SUM(Q10.C1),
           Q10."C2
         FROM
           (SELECT
              Q9.C1,
              Q9.C2
            FROM
              T1I AS Q9
           ) AS Q10
         GROUP BY
           Q10.C1
        ) AS Q11
      WHERE
        (Q11.C1 = Q8.C2)
     ) AS Q12