Symptoms

We have designed a workflow where in there is a task called "Cost Control". The destination Rule for this task is "Plan Just Once" and Slot is 1. PFA the screen shot for the same. The task is assigned to a Role (Group of users). All users are getting emails for the task. But when one user has opened the task, It is still showing as available on other users "My Tasks" view. It is showing as Available for the same user as well.

As per the forum threads, this type of destination rule definition should not be visible in other users "my tasks" once a user has taken the same.
http://community.k2.com/t5/K2-blackpearl/What-do-u-mean-by-Open-Status-for-a-worklist-item/td-p/53495
 

Diagnoses

Task not being opened in a way that assignes the task.
 

Resolution

Looking at the WF's provided I can see that you are using a Default Client Event to build up the URL to the SmartForm that the user will then use to access the Task ... However , simply hitting the Link will not automatically Open and Allocate the Task . This is done via the Rules on the SmartForm being opened . I do not currently have a copy of this , but can you please check the SF , verify that the Open WorklistItem rule on there is configured correctly and is indeed firing .

Reason being , a Task wont be allocated against a User until the Worklist Item has been opened by said User . As mentioned , opening the Worklist Item commonly gets assigned when a Task is opened via the Workspace Worklist , a direct Task Notification URL or when explicitly opened using a SF Rule