By converting the query from
select
new org.jbpm.task.query.TaskSummary(
...
t.taskData.actualOwner,
t.taskData.createdBy,
t.taskData.createdOn,
t.taskData.activationTime,
t.taskData.expirationTime)
from
Task t
left join t.taskData.createdBy
left join t.taskData.actualOwner
left join t.subjects as subject
left join t.descriptions as description
left join t.names as name,
OrganizationalEntity potentialOwners
where ...
to
select
new org.jbpm.task.query.TaskSummary(
...
a,
c,
t.taskData.createdOn,
t.taskData.activationTime,
t.taskData.expirationTime)
from
Task t
left join t.taskData.createdBy as c
left join t.taskData.actualOwner as a
left join t.subjects as subject
left join t.descriptions as description
left join t.names as name,
OrganizationalEntity potentialOwners
where ...
Now I am able to get the correct query result. :)