Query does not work in 11.2.0.3 release but works correctly in 11.2.0.1 release. In what could be th

Query does not work in 11.2.0.3 release but works correctly in 11.2.0.1 release. In what could be the reason?

WITH sourc(id, name, parent) as (select t.id, t.name, LAG(id) over (order by id) parent
                                   FROM (select 1 id, 'a' name from dual
                                          union
                                         select 2, 'b' from dual
                                          union
                                         select 3, 'c' from dual
                                        ) t
                                 )                 ,
     stepbystep (id, name,  parent) AS (select s.id, to_char(s.name),  s.parent
                                 from sourc s
                                where id = 1
                                union all
                               SELECT s.id, r.name||','||s.name,  s.parent
                                 from sourc s, stepbystep r
                                where s.parent = r.id
                              )
SELECT * FROM stepbystep