The query you mentioned in the description has a select clause with an implicit join:
"select p, p.department from Person p left outer join p.department"

The following does not use an implicit join at all:

from Cat as cat
join cat.mate as mate
left join cat.kittens as kitten

If there is a problem with the results returned from the above query, then I doubt it is related to your original issue (referring to an implicit join + an outer join on the same association).