Candidate-Groups

Hi,
I have a problem when seeking tasks using candidate-groups.
I created tarea1 which has associated candidate-groups "Group1, Group2, Group3.
Then I have a user "sebastian" which is a member of Group 1, Group 2 and Group 3.
The problem is that when I run taskService().findGroupTasks("sebastian");
I returned a list of 3 tasks equal, Tarea1, Tarea1, Tarea1. When it should be listed just once the task (Tarea1).
I'm not sure if it's a conceptual issue or a bug in the API.
I would be grateful for your help.

P/d: I'm not using swimlane because I had problems with respect to the Fork / Join.

Greetings. Sebastian