Adding the task listener is proving to have unpredictable results.
(This has been tested using task listeners on a usertask, which runs an expression on the create event)
For example, with a very simple diagram with only two user tasks and a start/end event:-
I can add a task listener to userTask1 and it will save two copies of it.
I will delete the extra task listener and go to add a new (different) task listener to userTask2.
When I input the expression into the listener configuration window and click ok, it will save it on some other task (in this case userTask1 as it's the only other task).
I can then remove this from userTask1 and go back to userTask2 to re-add it there and I will find that it has copied over the listener that should be on userTask1 so that I have the same task listener on both tasks.
Sometimes I end up with the same task listener being copied to multiple usertasks, other times I end up with all my task listeners on a single task.
If I then go in to the code (diagram xml) I can alter the task listeners and everything is fine and the model acts as it should.
I use the task listeners to run an expression on the create event of the user task to update a variable.
This has been tested on both Kepler and Juno, both with the same results.
This issue can be seen on Eclipse Kepler and Juno.
OS Win 8